Tài liệu Oracle Unleashed- P20 doc

Previous Page TOC Next Page Home ● 53 ❍ Networking ■ Quick and Dirty Introduction to Networking ■ Overview of Oracle Networking ■ ODBC Versus OLE ■ Other Middleware Vendors ■ Some Sample

Previous

Page TOC

Next Page Home

● 53

❍ Networking

■ Quick and Dirty Introduction to Networking

■ Overview of Oracle Networking

■ ODBC Versus OLE

■ Other Middleware Vendors

■ Some Sample Configurations

■ Network Development Tips

The good news is that client/server and networking to access databases has moved beyond the point of radical, new technology and into the realm of the stable production environment Sure, you have to pay some dues to learn the new terms and understand what hardware and software components you are using to get your information I, for one, never want to go back to the days of the dumb terminal when it comes time to write a production application Very few

business users can be "wowed" by the traditional terminal interface where they have to learn to navigate through a series

of menus or enter commands at the command line

This chapter has an ambitious goal of providing you an understanding of networking as it relates to Oracle databases Because many users are inexperienced in modern networking environments (using a Novell server to print your

documents does not count), the terms serve as an initial stumbling block that you must overcome The next layer of complexity comes from the fact that there are a large number of people out there designing network components There are a few standards out there, but a number of vendors are competing with one another to set "the" standard You need to

be aware of the common products that are out there and how they work Finally, Oracle itself presents a number of networking challenges The challenge comes from Oracle's large customer base that has many different needs As a result, Oracle offers a wide range of products that you might have to become familiar with, depending on what you need

To approach these problems, I divided this chapter into the following sections:

● A quick introduction to some basic networking concepts

Please purchase PDF Split-Merge on www.verypdf.com to remove this watermark.

● A discussion of the basic types of networking that you might encounter in your Oracle systems

● Some coverage of the more common alternative database networking architectures

● An overview of SQL*Net, Oracle's most basic networking product family

● An introduction to some common middleware products (the software that enables your applications and

databases to interface with your networks)

● An overview of how you can use gateways to connect Oracle to non-Oracle databases, such as IBM's DB2

● A presentation of some sample database network configurations to give you a feel for some working

environments

● Finally, some tips on developing and implementing network database environments

Because this is a challenging amount of material to cover in a limited number of pages, I should get started

Quick and Dirty Introduction to Networking

Although it might seem too basic to some of you, I thought that I would define a computer network as a collection of hardware and software that enables multiple computers to communicate with one another Network engineering types might think of more precise or elegant definitions, but I think that this is good enough for our purposes here Figure 53.1

is a basic drawing that illustrates this definition The concept is quite simple You have two or more computers that are connected together in a manner to exchange information Later in this chapter, I will go through the details of different network transmission standards and all of those annoying details However, for now, focus in on the basic concepts of computers and a network that somehow connects them together

Figure 53.1 Basic concepts behind a computer network

As mentioned in the introduction to this chapter, part of the problem in setting up networks to support databases is dealing with all the components, versions, standards, and so on that exist in the networking market The network folks have designed a very useful tool to diagram this process They use a stacking diagram that shows various layers of functionality and how they stack on one another to build a complete network connection They typically use a seven-layer model, which details more of the networking environment and also supports a wide range of application uses Although their model makes an interesting discussion, in the interest of efficiency, I have simplified the model to deal more closely with the database networking models that you will come across This database seven-layer model is shown

in Figure 53.2 Networking purists might argue that I sometimes combine layers of the traditional seven-layer model and split a layer into two layers However, this is how Oracle and other vendors tend to bundle their products, therefore it is

an easier way for a DBA or developer to view networking

Figure 53.2 Seven-layer database network stacking model

The lowest layer is the networking transmission system Typically, your local computer networking staff arranges this for you The transmission equipment is designed to transmit the signals between computers It usually transmits only a limited range of transmission formats (types of signaling) and protocols (the addressing and packaging of the

transmission) It also tends to limit the types of physical connections that you can use to tap into the network with your network interface cards Because this part of the network is usually arranged for you, it can actually help narrow down the large number of possibilities that you have to consider; as a result, the transmission formats and protocols are an excellent place to start when designing your systems

The second layer up provides the physical and electronic interface between your computer and the network transmission system This layer consists of some cabling and a network interface card that plugs into your computer With servers,

you typically do not have a lot of choices for a network interface card (usually one or two cards per transmission

protocol) With PCs, you have a large number of choices for the various transmission protocols The most important thing to ensure is that the card you choose is compatible with your operating system (especially when you are using newer operating systems such as Windows NT and Windows 95)

The next layer to consider is the transmission format This layer tracks when your computer can make a transmission on the network and ensures that the signals are correct so that other computers can detect them The transmission format is typically the domain of the electronics engineers who worry about signal voltages and such details There are three types

of common transmission formats:

● Ethernet: This is perhaps the simplest and most common signaling format With this format, everyone transmits their signals onto a wire whenever they want to, and the systems detect and resolve any conflicts that arise Typical speed is 10 million bits per second (bps), which is limited to about 3 million bps as a sustained transmission rate A 100 million bps version is starting to appear on the market

● Token Ring: With this network transmission format, everyone transmits signals when it is "their turn." Ring networks are popular in IBM environments with their speed of either 4 or 16 million bps

Token-● ATM (Asynchronous Transfer Mode): This is a newcomer on the market It is not common in local area

networks (LANs) yet, but many manufacturers are starting to design and sell adapters using this technology ATM relies on relatively high-speed burst transmissions

The fourth layer (the transmission protocol) is similar to the envelope in which you send a letter by mail This layer assembles the data you're transmitting into packets that can be routed through the network Some of the more common transmission formats include the following:

● TCP/IP (Transmission Control Protocol/Internet Protocol): This is the basis of the Internet that you have probably read about It started with a U.S Government research project and turned out to be a standard that people could rally around TCP/IP is the most common format that I have come across for client/server computing and connecting to UNIX-based computers

● IPX/SPX: These are the transmission protocols used in Novell networking environments Their use is typically limited to communications between PCs and Novell servers

● NetBEUI: This is a protocol that some IBM and Microsoft networking products use for basic communications between PCs and LAN servers (such as Microsoft Windows NT) You will probably only encounter this protocol if you are running the workgroups version of Oracle

I've had trouble using NetBEUI for client/server communications I recommend that you consider using TCP/IP for client/server applications

● SNA (System Network Architecture): This is actually more of an architecture than a protocol It is the main environment for IBM mainframe shops

The fifth layer is where the database-unique processing begins; I call it lower middleware Middleware is a term that you encounter often in database networking It refers to any supporting software that you need to connect your application or database management system to the networking utilities on your computer I made up the term "lower middleware" to refer to products such as Oracle's SQL*Net that transmit database requests in a predefined format (such as TCP/IP) to the networking software on your host computer

The next layer is what I call upper middleware These products are designed to enable a variety of applications to interface with lower middleware products to interface with a database on a remote computer Upper middleware is how I qualify Microsoft's ODBC (Open Database Connection) standard, which takes queries and transactions from products such as the Visual C compiler or the Microsoft Query product and formats them to interface with a specific lower middleware product such as SQL*Net Some products, such as Oracle's SQL*Plus, already have a direct interface to the lower layer of middleware (SQL*Net) and therefore do not need a separate lower middleware software package

Please purchase PDF Split-Merge on www.verypdf.com to remove this watermark.

Finally, at the top of my stacking model are the applications that most users really care about Of course, on the server end is the database management system On the client end is the financial accounting or sales forecasting system that the users interact with on a daily basis As I discuss later in the chapter, you have the option of using the PC and network to emulate a dumb terminal In this host/terminal scenario, the PC application that you run is a terminal emulator that connects directly to the network transmission utilities

Why did I go through the previous discussion? One of the greatest challenges that I have faced in integrating computer systems is getting all the drivers, network interface cards, operating systems, middleware, and application packages to work with one another Don't be too alarmed They work very reliably once you purchase the right components The trick is figuring out the right equipment and software and configuring them properly

Figuring it out is where the database seven-layer model comes in handy Each of the layers corresponds to a product that you have to purchase Your trick is ensuring that whenever two layers touch one another, the products on either end are compatible This compatibility has to be specific to your host computer environment (for example, a Hewlett-Packard H50 UNIX server or Packard Bell Force 101CD running Windows 95), and the exact versions of the products on either side must be compatible with one another (for example, SQL*Net TCP/IP Version 2.3 for Windows 95 and the

Microsoft Windows 95 TCP/IP stack) Sales people tell you that the products work with a particular environment, but they might not know the "gotchas"—if you can only use a particular network interface card, for example When you're picking products, I recommend that you draw out your database seven-layer stack and look at the product specifications

to ensure that all components are compatible with one another

Overview of Oracle Networking

How does Oracle fit into the networking picture? The good news is that Oracle provides a large number of networking options (unfortunately, for the systems folks and DBAs, that is also the bad news) Oracle started out as a host-based application However, the company quickly recognized the advantages of splitting processing between the host

computers and the increasingly intelligent workstations and PCs that were appearing on user's desks This lead to client/server products such as SQL*Net and PC development tools such as Oracle Forms The client/server environment evolved to include interfaces to non-Oracle development tools and databases through the neutral ODBC and OLE

interfaces, which I discuss later in this chapter Finally, databases have grown in number and size With a single, huge database to process information, many organizations have elected to build a series of smaller databases that are

connected to one another This is where the Oracle SQL*Net, Distributed Options, and Gateway products come into play I discuss each of these concepts in more detail in the next few sections Figure 53.3 summarizes the Oracle

networking environment

Figure 53.3 Oracle networking overview

Before I leave this discussion, I want to point out something that I always considered a little bit odd If you are working with the Oracle Workgroups Server products on a Microsoft Windows NT server, you actually use networking software

to communicate from your regular Windows applications (such as SQL*Plus) that are running on the NT server to your Oracle database, which is designed to run in native NT mode This happens because regular Windows applications run under an NT subsystem knows as Windows on Win32 (WOW) Oracle linked the 16-bit and 32-bit sides of the Windows

NT system via SQL*Net If you use Named Pipes as your communications protocol, you do not need to have a network interface card installed, but if you use TCP/IP as the protocol, you must have a network interface card It's just something

to remember if you are working in this environment

Host/Terminal Connections

A good place to start is where Oracle started—with databases located on host computers that are accessed using

terminals (or PCs that were acting as terminals) Figure 53.4 shows the basic configuration of the architecture; it has the blessing of being very simple The host computer system provides facilities to connect terminals and supports one or more terminal types (such as DEC VT-100) to which it can send output and from which it can receive input This type of

connection usually has the following characteristics:

● The interface is usually capable of displaying only text and not graphics

● You typically control the interface through a series of menus or command-line inputs

● You do most of the data entry via forms that rely on function keys or tabbing to special fields that confirm you are ready to enter data

● The host computer performs all of the processing, which includes the display of information, the business calculations, and the database management system processing

● You usually write the applications using form-generation applications for user interaction and report-generation utilities for printed reports

● In many cases, the user interactive processing is supplemented with a series of batch reports that run at certain times of the day/week/month which users read through to obtain the information that they need

Figure 53.4 Host/terminal networking

Client/Server Connections

Do you hate the buzzwords that float through the computer industry? Client/server must be one of the most frequently used (and misused) words in the computer industry Once upper information systems management gets a buzzword in its head about the ultimate solution to all problems in the computer industry, you can bet every salesman out there is going

to scramble to find a way to say that his product is an implementation of that buzzword Client/server is no exception to that rule of buzzwords

The host/terminal architecture dominated the industry for a number of years and its use continues today; however, it ran into some limitations Some argue that the big host computer vendors became a little lazy and stopped turning out new equipment at a rapid pace Others argue that as the processing load continued to grow, it became impossible to build computer processors that were powerful enough to keep up with demand Still others argue that the large computer vendors never produced enough units to keep the cost per unit down

Whichever reason you prefer (or even if you prefer to think that it was a little bit of all these reasons), the client/server architecture has grown over the last decade to become a very popular alternative to the traditional host/terminal world

Oh, a lot of shops still do not consider anything other than mainframes, COBOL, and terminals; however, because you are reading this book, you are probably not in this group Now, I cover client/server in a little more detail

Forming a definition is a good start to this discussion Because I am not much of a theorist, I will stick to a simple definition I define client/server architectures as systems where the computer processing load for a single application is distributed between multiple computers In host/terminal computing, the terminal (or PC emulating a terminal) is only responsible for the presentation of the information You can cite a number of examples that fit my definition which you might not want to call client/server, but it gives you the general idea Figure 53.5 illustrates this general concept

Figure 53.5 Client/server networking

With a definition this broad, you could have a number of different distributions of labor that still qualify as client/server Going back to my buzzword discussion, that is why you see a large number of different vendors with widely different products and architectures all claiming to be client/server I guess that is part of free enterprise or something like that What might be useful now are some sample distributions of labor that advertise themselves as client/server, as shown in Figure 53.6

Please purchase PDF Split-Merge on www.verypdf.com to remove this watermark.

Figure 53.6 Sample distributions of labor in various applications

As you can see, there are a number of ways to split the application Some of your choices in designing your architecture are limited by the tools you choose (or vice versa) You might want to split up your processing based on the relative capacity (or costs) of your standard server and client platforms You might also find that your users' demands for

graphics and response time influence your decisions For example, if you have a group of users who demand excellent graphical interfaces and fast performance, you could buy a moderately powerful server and some high-end PCs As another example, if you already have an overloaded but paid-for host computer and reasonably powerful PCs, you could extend the life span of the host by converting some of your applications to perform the database processing You could perform some of the calculations on the host server and then perform the rest of the calculations on the client The following are some general characteristics of most client/server environments to consider:

● You use graphical user interfaces (where the users can access information using a mouse to click a button on the screen or select an item from a scrollable list) to interact with the users

● You have a wide range of tools and connectivity products to choose from This can be a blessing in that you have the capability to preview a number of different products to see which one is best suited to your individual needs It can also make the task of integrating products a bit more challenging

● The capabilities of the client workstation become an important factor in the overall application performance Because most organizations have PCs that vary somewhat in computing and memory capacity, you might find that you have to upgrade certain PCs in order to run your new client/server applications

● The capacity of the network (especially wide area network links used to connect different facilities) can be an important factor in determining the overall performance of the applications

One final concept that you might need to consider is the difference between two-tier and three-tier client/server

architectures When client/server first started, you had just two machines (the client and the server) The client typically performed the display functions, and the server did most of the calculation work and database management People liked the display capabilities of the PC but found that neither the PCs nor the server had sufficient processing capacity to perform complex calculations that might be necessary for detailed financial analysis or other such needs These users did not want to move up to the more expensive larger computers (twice the processing capacity usually has much more than twice the price in the computer industry) Instead, developers came upon the idea of splitting the processing load for a given user and application among three different computers The client machine still performed the user interface work; however, the other work was split between a database server and an application server The database server focused on running the database management system, and the application server performed all the computations associated with the application (See Figure 53.7.) The three-tier architecture is more complex to design and configure, but it can be the answer if you perform a lot of demanding computational work but do not want to invest in a single large computer

Figure 53.7 Two-tier and three-tier client/server architectures

problems)

Figure 53.8 Database links

Overall though, this first phase was a good start on splitting up the database processing work load; however, other issues soon became apparent The biggest issue was that remote locations usually had to rely on a relatively slow wide area network communications link to access a database located on a centralized server Another factor was that programmers had to be aware of all the database links and put them into the SQL statements they issued

The next generation of database-to-database connectivity came with Oracle's distributed database option (option means that you had to pay extra for it) With remote field offices that are connected to the central office by relatively slow communications lines, you could implement smaller servers in the field that get a nightly download of data from the central server You would then write batch routines that ran at night, figured out which records needed to be

downloaded, and so on You could do this yourself, but it is much easier if the database management system takes care

of this stuff for you That is the idea behind the distributed database option

There are two general features of such a system First, you can access tables located on remote databases as easily as you access tables located on the disks that are attached to your local server Second, if you have multiple copies of the data to speed up processing at remote sites, you can set up the system so that Oracle synchronizes the data between the systems Actually, quite a bit of logic goes into ensuring that if you make a change in a particular record, it is applied to all the copies of the database—especially when some of the changes might take minutes or even hours to finish It is much easier to put that burden on Oracle rather than code it into your application There aren't a huge number of installations out there using this option, but it could be very useful in certain cases Figure 53.9 illustrates the Oracle distributed database concepts

Figure 53.9 The Oracle Distributed Option

Assume you have linked multiple Oracle databases that are located on different servers to distribute the database

processing load of your organization What more can you ask for? You now have the ability to take advantage of the large number of PCs sitting on people's desks, you can have multiple servers (located wherever you need them in your wide area network) performing the database management tasks, and you can even use a three-tier client/server

architecture to distribute complex computational loads to a different server Well, there is one other possibility that Oracle sales representatives usually do not like to consider What if you have a lot of data on DB2 that you do not want

to convert to Oracle, or what if you have a subsidiary or business partner that has adopted VAX RDB as its standard database management system?

The answer to this question comes in the form of gateways Oracle makes a series of gateways that link Oracle databases

to DB2 and other major database products It seems reasonable that Oracle will continue to work in this area to increase the number of gateways to other vendor's databases The key to these gateways is that they are conceptually similar to the distributed option All you (or your DBA and system administrator) have to do is install this gateway product and provide all the configuration information about where the data is stored, what format it is in, how you network into the database, and so on The gateway software then takes care of the details whenever your applications issue a query or transaction that affect data in these remote databases As with many of the networking products discussed in this chapter, the gateways are not for everyone, but they can be a big help to those who need them

Just for the record, many of the other database vendors and third-party developers have gateways that connect to Oracle databases They have seen the same market opportunities to sell software to organizations that are not planning to convert all their databases into Oracle systems The key to picking the right gateway is to ensure that it supports the versions of the databases you are using and that it fits into your computer and network architecture These gateways are relatively new products, and I would suggest checking with other customers who are using the products or perhaps even setting up a test system in your organization before you commit to purchasing the gateway as the ultimate solution to all your problems

Please purchase PDF Split-Merge on www.verypdf.com to remove this watermark.

SQL*Net Version 1

Now that I have covered the general concepts of database networking, it is time to get into some specifics A good place

to start is with SQL*Net Version 1, which was the first product in the Oracle environment to support networking

Designed to support client/server computing and database links, SQL*Net Version 1 was a good start on this process and was fairly reliable In fact, I did not start using SQL*Net Version 2 until recently, so that is some indication that

SQL*Net Version 1 was not a bad product

SQL*Net is a product that I classify as lower middleware It does not alter the format of the query to comply with Oracle standards or handle the details of transferring the results into a format that the applications can handle Instead, it sends and receives data in the format that it understands and lets other middleware or the applications themselves get that information into its format Some applications are designed to interface directly with SQL*Net Oracle's database

management system, SQL*Plus, Oracle Forms, and its other development tools are all designed to interface directly with SQL*Net You can develop applications using Oracle's precompilers and products such as Oracle Objects for OLE that interface directly with SQL*Net Figure 53.10 shows this direct interface

Figure 53.10 Products interfacing directly with SQL*Net

You might have noticed in the last paragraph that the word Oracle preceded most of the products that I listed Although there are third-party products that are designed to interface directly with SQL*Net (such big names as PowerBuilder), many other developers yearned for an "open" standard that would enable them to write one application that could

interface with a number of different middleware packages and database management systems This is how the products that I call upper middleware were born

The basic concept is simple Design a product that has a neutral, published interface from applications and then design a neutral interface and connection software for a variety of lower middleware transport protocols Figure 53.11 illustrates this concept One of the ways that you can tell a good idea in the computer industry is when every big company jumps

on an issue and creates their own "industry standard" to implement the concept Such is the case with what I call lower middleware

Figure 53.11 Upper middleware interfacing with SQL*Net

The biggest name in this market that I have encountered in my experience is Microsoft and the Open Database

Connection (ODBC) standard It has the advantage of accessing a large number of clients (PCs that run Microsoft Windows, Windows NT, or Windows 95) It also came out early in the client/server evolution process and so there are already a number of applications written with this standard Finally, Microsoft provides a series of drivers and utilities with most of the operating systems delivered, so you can keep the cost of an installation down (you would be amazed how fast the cost of a client workstation can go up when you start buying a large number of "optional" packages)

This is not to say that Microsoft is the only upper middleware vendor on the market There are a number of vendors such

as Intersolv and Openlink that have worked to produce drivers that are faster than the standard ODBC drivers or that work with more database management systems Once again, you are faced with a number of choices One is a low cost solution; the others might provide improved performance Still others, such as Openlink, merge the functionality of SQL*Net with an ODBC driver to reduce the number of middleware products that you need to install and maintain

I have one final note to add about middleware Just when you were confused enough with the various options related to ODBC, Microsoft throws in another wrinkle They incorporated the concept of upper middleware into a structure that enables you to dynamically share data between applications and even launch one application from within another This standard is called Object Linking and Embedding (OLE—you know there had to be an acronym for it) Anyway, I discuss the differences between ODBC and OLE later in this chapter For now, you should understand SQL*Net as a lower middleware product and how it interfaces either directly to SQL*Net-ready applications such as SQL*Plus or the Oracle database management system and upper middleware products such as Microsoft's ODBC

Next on the agenda is a discussion of how SQL*Net is implemented Once again, there is more than one answer

Remember: part of the sales appeal of Oracle is that it works on a wide variety of computer systems and is designed to

do many things For this discussion on SQL*Net, I split the discussion of implementation into two separate discussions The first discussion is about SQL*Net on computers (such as UNIX or VAX VMS) that run multiple processes at the same time The other discussion covers SQL*Net on computers that are basically single tasking (such as Microsoft DOS and Windows 3.1)

On multitasking computers (those running multiple processes), Oracle SQL*Net Version 1 is implemented as a listener process Listener is a good name for this process It merely sits there in background and listens for someone to send a signal into it This signal could come from either the remote machine, in which case it picks up the signal from its interface to the network transmission protocol, or from the local application or database When it is connected to the database, SQL*Net spawns (creates) a server process to handle the interface to the database management system and merely passes signals between this database interface process and the network drivers Figure 53.12 illustrates the basics

of this configuration

Figure 53.12 SQL*Net Version 1 implemented as a server process

Microsoft Windows 3.1 and DOS do not support multiple background processes As a result, Oracle had to adapt its SQL*Net Version 1 product to fit within this environment The problem is that memory is usually in short supply on PC clients, so you do not want to waste memory space by permanently loading the SQL*Net drivers To get around this problem, Oracle uses a Dynamic Link Library (DLL in computer-speak) The software is loaded into memory when needed to facilitate communication between the applications and the network protocol drivers This can actually be more convenient because you do not have to worry about starting and stopping the background SQL*Net listener process under this architecture Figure 53.13 illustrates the SQL*Net DLL concept under Microsoft Windows 3.1

Figure 53.13 SQL*Net Version 1 implemented as a DLL

There is a lot that I could discuss regarding SQL*Net Version 1; however, because you might not even use this version

of the software and it is usually transparent to developers and end users, I want to cover only one more topic: controlling and using the SQL*Net Version 1 listener process As I mentioned earlier, if you are using SQL*Net under Microsoft Windows 3.1 and everything is set up correctly on your computer, you load the SQL*Net software automatically when needed On computers where SQL*Net is a background process, you have to ensure that the background process is running before you use SQL*Net

The good news is that Oracle provides relatively simple-to-use utilities to determine the status of this background

process, start it, and stop it The bad news is that you have to know the name of the process and the way to access it To

start off with, process is a term that works under UNIX Under Windows NT, the more proper term is service Novell refers to Novell Loadable Modules (NLMs) For the name of the process (service or whatever), you need to see what

name your database administrator set up when installing the software Which utility controls the background process is also important to know Under Windows NT, you access the Services Utility under Control Panel to start up the service Under UNIX, you use the tcpctl utility (with the start, stop, or status options) to work with the SQL*Net TCP/IP

background process The best advice that I can give you with the wide variety of configurations available is to check with your database administrator, system administrator, or whoever installed your SQL*Net software

Finally, the topic that is most interesting to the average user is using SQL*Net Version 1 to access remote databases This process is relatively simple; all you have to do is specify the database address in the manner appropriate to your application The SQL*Net Version 1 address is composed of three parts The first part tells SQL*Net which protocol you are using (T = TCP/IP, P = named pipes, and so on) The second part of the address shows which computer the desired database is on In TCP/IP, for example, you can either use an alias defined in the hosts table (such as marketing) or the Internet address of the server (such as 10.15.20.25) Finally, you need to specify the SID (Oracle's system ID) for the database that you want The SID is set up by the DBA when creating the new database, so that person has to tell you the name of the SID

Please purchase PDF Split-Merge on www.verypdf.com to remove this watermark.

SQL*Net Version 1 enables you to create aliases for your remote databases It also enables you to define default local and remote databases that are accessed when the user does not specify the desired database The following is a sample call to the SQL*Plus utility that accesses the jdoe account in the MKT Oracle instance on the marketing server using the TCP/IP protocol:

following:

● In SQL*Net Version 2, the DBA has to prepare a series of files that contain all the connection information for the various data sources that are available These data files associate a simple alias (such as main_sales) with all the information such as the SID, host computer, protocol to use for communication, and so on All the users have to worry about, once they get copies of these files from the administrator on their computers, is what the aliases are and what information is stored in each of these databases

● SQL*Net Version 2 can interface with a feature of the Oracle7 server known as the Multi-Threaded Server In Version 1 of SQL*Net, you allocate a dedicated process for each user who connects to Oracle via SQL*Net This process stays open until the user disconnects, which could be the end of the day for some users This can become a problem when you have a large number of users accessing a system where they might be connected to their application all day even though they are not actively working with the database The Multi-Threaded Server concept enables the SQL*Net users to share a series of server processes, each accessing the server process only when he has an active query or transaction

● The later versions of SQL*Net Version 2 are much better at detecting when a user gets disconnected from Oracle without issuing a proper command to disconnect (for example, if they get bored and hit Ctrl-Alt-Delete

in the middle of a long query) Under SQL*Net Version 1, this can cause a shadow process to hang around eating up large amounts of processor time (these processes run away and can take up the entire CPU) SQL*Net Version 2 has some time-out parameters that enable you to eliminate this problem

● The names of the controlling processes are different between the two versions of SQL*Net so that you can easily tell which version is running

● Finally, you really should use the Oracle network management tools to create the configuration files You could edit the aliases in the old SQL*Net Version 1 files if you were ambitious (the default remote connection, and so on) However, unless you are really sure of what you are doing, use the Oracle utilities to make your network configuration files They are somewhat complex in syntax and the names of the fields are not always obvious

SQL*Net Version 2 is a sound product that provides the same basic services as SQL*Net Version 1 I caution you to allow adequate time to get SQL*Net set up properly I have found that it always takes longer than you think it will to set

up the SQL*Net configuration files correctly, start the background processes, and complete any upper middleware configurations such as ODBC Even after you have done it several times, there seem to be a few quirks about each new type of server or each new network stack on the clients

ODBC Versus OLE

Earlier in this chapter, I gave a brief introduction to ODBC and OLE, two standard upper middleware package standards created by Microsoft There are other vendors who have created their own ODBC software packages because that is a utility that is separate from the basic operating system I am not familiar with any users who have created their own version of OLE; however, Oracle has created Objects for OLE, which enables you to write software that uses OLE to interface with an Oracle database

What are some of the differences between ODBC and OLE? The biggest, in my mind, is that Oracle supports OLE, and many of the other big database vendors do not As a result, if you are writing an application that you want to sell to a broad audience with multiple database management systems, OLE might limit your options Also, because ODBC is older, you might be able to find more third-party development software to support your development effort

Most of the folks I have talked to indicate that they found OLE several times faster than ODBC Some people on the ODBC side might counter that the initial Microsoft ODBC drivers were not as optimized as they could be and that you can increase ODBC performance by a good bit Some of the OLE concepts (such as launching a small database

application from within a word processor or spreadsheet) are very difficult to implement using ODBC In summary, I see OLE as far more capable in the long run, and ODBC as more practical in many circumstances, at least for the next year

or so

Other Middleware Vendors

Another point I mentioned earlier is that there are other middleware vendors you might want to consider Why? Perhaps you are working with an operating system such as Windows 95 right after it was released, and all the beta test drivers that you were shipped are buggy You desperately want to get a product out the door, and you are searching for that one driver that will enable you to complete the porting of your software package to Windows 95 Also, you might be in a situation where you are writing an extremely demanding application, and you are pushing to optimize performance whenever possible In this section, I present a brief overview of some of the middleware vendors on the market to give you a feel for some of the alternatives After this book goes to press, another vendor might release a great product that could be the one that is right for you You should perform the usual research steps (vendor search, magazine reviews, and so on) to see what products are available to you

I'll start the product review with the products from Oracle shown in Figure 53.14 The basic middleware that Oracle provides is the SQL*Net product, which I classify as lower middleware Oracle also offers its own set of ODBC drivers

to compete in the upper middleware market The Oracle ODBC drivers provide an interface to Oracle databases, so if you are trying to write applications for a wide variety of databases, you might still need to purchase additional ODBC drivers for those other databases One thing to consider when working with new releases of Oracle is that the Oracle drivers might be more up to date than some of the third-party drivers, although the ODBC standard shields you from some of the internal changes that occur in the databases themselves Oracle also markets its Objects for OLE product to serve as upper middleware for those who want to use OLE

Figure 53.14 Middleware products from Oracle

Of course, Microsoft wrote both the ODBC and OLE upper middleware standards The Microsoft development tools come with ODBC drivers and OLE support, in addition to development tools from other third-party vendors These products compete with the Oracle ODBC drivers and Objects for OLE Microsoft supports networking to its SQL*Server product as part of the operating system, so I guess you could call Microsoft's drivers lower middleware for a non-Oracle database

Next on the list of representative vendors is Intersolv What I have worked with is their ODBC drivers They provide drivers for a range of databases, often before the database vendors come out with their releases They also have the distinction of writing the drivers that are provided by some of the other database vendors Intersolv owns the Q+E product line, which was one of the first tools that enabled you to connect spreadsheets such as Microsoft Excel to remote databases Again, the main focus for Intersolv is the upper middleware ODBC market

Please purchase PDF Split-Merge on www.verypdf.com to remove this watermark.

Last on this short survey of some of the vendors in the middleware market is a British firm called Openlink They are somewhat unique in that they bundle together the functions of upper and lower middleware into a single package You have to run their products on both the client and the server, but in return, you get to avoid installing and maintaining a number of lower middleware products The basic architecture is shown in Figure 53.15

Figure 53.15 Openlink combined middleware concept

Before closing this section, I want to mention that there are other standards out there competing in the middleware market Several vendors in the UNIX and Apple worlds favor different standards that are similar to ODBC and OLE Each touts the benefits of their framework over the others If you spend a lot of time working in one of these

environments, you might want to consider these competing standards However, if you primarily use PCs as clients, ODBC and OLE are the two standards that you will encounter the most I view it as though I am living with the

standards set by the industry and not making them If a standard is adopted by the rest of the computer industry, it does not matter how many wonderful features the competitors have; they will probably fade away due to lack of sales in a few years The only difficulty that you face is figuring out where this fickle industry is headed

Some Sample Configurations

So far in this chapter, I cover most of the networking topics that you probably need as a developer or user of a networked Oracle system What is missing is that one single drawing which shows you all the pieces you need to buy for this networked Oracle system I can't provide that drawing because, as I mentioned earlier, there are too many different options You can now use Oracle development tools with non-Oracle databases and vice versa What I thought would be useful here is a series of sample configurations that might give you some ideas about what working networked database configurations look like

I have one big note of caution You have to look at each type of system configuration on an individual basis There are

so many unusual reactions between different versions of the various products that you really should test things in your environment before you can be certain that it will work There are things that you might not anticipate—for example, if none of the wide area network transmission equipment in your company is capable of transmitting the TCP/IP protocol

or something really strange such as that Anyway, enough said; just test everything out using demonstration software or limited quantities whenever possible before you commit to rewriting your entire application architecture using a given set of products

With that traditional cautionary note out of the way, look at the first sample configuration Because I started my

discussion of network access to database with the host/terminal architecture, I thought that I would present an example

of this environment (See Figure 53.16.) Note that even though I use PCs to access the VAX Oracle database, they are emulating dumb, non-graphics terminals The applications developed use the traditional, character-based interface where you hit F3 to commit your changes or F4 to exit out from where you are Note that all the application development software and completed applications reside on the Oracle server (in this case a VAX) and that the linkages from the application to the database management system are already set up (you do not need to configure any links as you would

in SQL*Net)

Figure 53.16 Host/terminal example

Next on my list of samples is a basic client/server system, illustrated in Figure 53.17 In this case, I show the Oracle tools set (which now goes by names such as Developer/2000 and Oracle Forms, but who knows what the marketing folks will call it next year) on PCs interfacing with an Oracle database on a UNIX server Some key points to note about this architecture is that you do not have to use an upper middleware product on your clients (because these tools are all designed to interface directly with SQL*Net) Oracle tools have recently started to also support an ODBC interface I guess Oracle wants to sell its development tools even to customers who use other database management systems

Figure 53.17 Oracle development tools interfacing with an Oracle database

Next, I cover a system that uses upper middleware—in this case, ODBC—to interface with an Oracle database located

on a UNIX server, as shown in Figure 53.18 This environment uses the Microsoft C++ compiler with a set of third-party ODBC drivers from Intersolv The database is Oracle 7.1, located on a Sun UNIX server One key point to note from this example is that you must ensure that your ODBC driver is compatible with the exact version of networking software that you are using (you might have trouble, for example, if you move your application to Windows 95) Also, when using a development tool such as C++, you must be sensitive to details such as the data types that the ODBC driver is returning

to your application (it does not map to character, VARCHAR, and NUMBER, as in the Oracle database) This detail work can take up some time, so you might want to run some tests up front to figure out the calls and returns that you will

be dealing with

Figure 53.18 Example of an ODBC environment

Finally, I thought it'd be useful to include an example of a distributed database environment I have not encountered a large number of these configurations, but that could change in the future as gateway and distributed database processing technology continues to improve Figure 53.19 illustrates one such system The basic concept behind this system is that the two databases (perhaps one is in Cleveland and the other is in Chicago) are linked together Users interact with their local database and let the distributed option take care of ensuring that the remote database is updated Delays in the transmission of the database between the systems do not delay the user's processing

Figure 53.19 Example of a distributed database environment

Network Development Tips

Here, I summarize some of my experiences dealing with networked database environments into a series of tips Think of this information as highly condensed examples Anyway, I urge you to at least consider the following directions:

● I first recommend that you do not cheat and try to implement the production environment late in the

development cycle It is tempting to say that you will develop everything on a stand-alone workstation and then convert it to the client/server environment the week before testing (you can certainly get it working in a week, right?) Anyway, I like to spend the time getting the true working environment set up in the beginning for several reasons First, you might find that some of your drivers and products are incompatible You might have

to troubleshoot and then order replacement products, which can take an amazing amount of time Also, your developers need immediate feedback during development when they write software that is not optimized for the end-user environment For example, imagine a piece of code that pulls down to the PC all the data from a very large table (with lots of long text fields) located on the server just to calculate the sum of a single number field This code would be extremely slow over a busy network The developer could use a built-in Oracle sum function and only have to return a few bytes of data with the result

● Now, I give you a recommendation where I do not always practice what I preach I recommend that you do not deviate from common computer environments and tools I like to live on the bleeding edge of technology, but that makes it extremely challenging to get those production applications out on time Incompatibilities of drivers and tools with new operating systems such as Windows 95 requires that you have a fair amount of experience dealing with lower-level system details and a wide range of access to vendors In an ideal world, you would have a lab environment where you could test and get new products working and then use them in your production and development environments

● Know about your network monitoring and testing utilities Many errors, especially those in the client/server environment, translate into something similar to "There is something, somewhere that is not right." I hate those error messages but must live with them What you then do is use some of the low-level testing utilities to go step by step through the system to see where the problem lies For example, if I am setting up the C++/ODBC

to UNIX database via TCP/IP environment and encounter a problem, I have to use several utilities to test the connection I typically start by using the ping utility that is common to most TCP/IP environments to ensure

Please purchase PDF Split-Merge on www.verypdf.com to remove this watermark.

that I have basic networking connectivity between the two computers I then use Oracle Net Ping to see if my two SQL*Net processes are communicating with one another Next, I use an easy ODBC access tool such as Microsoft Query to see if I set up my ODBC configuration correctly Finally, I create a new Visual C++

application using the App Wizard to see if I could access the database from a basic C++ environment (if I get a table list when selecting the data source in App Wizard, it is a good sign that ODBC is set up correctly)

Anyway, as you can see, you might have to use a number of products to see where your problem lies What you are trying to do is find a simple tool that tests each of the interfaces in the network stack one at a time, starting

be as simple as needing a special patch from a specific vendor if you have a certain old model of PC

● Have help lined up in advance when possible This can take a number of forms Perhaps you can have a local vendor or contractor who has done this before come in to help you set things up You should also have support from the product vendors, at least during installation It is very useful to keep all those books and purchase order copies in a file so that when you have problems, you can get the answers you need quickly

● Bring in all your local experts from the start This list of people might include network administrators, system administrators, database administrators, and others If they participate in the process when you are ordering and setting up the configuration, they can often save you a fair amount of time and money They can tell you little things such as "We are on Novell 3 now, but we will be upgrading to Novell 4 next week so you'd better be ready for it." Most information systems shops are so busy that it is often impossible for any one person to be aware of all the things going on Get input from the individual experts early and often

● Start with simple applications when moving to a new environment You could try to make your first client/server application the mission-critical executive information system that the CEO and all the vice presidents use every day If so, you have a lot more guts than I do One example of a good first system to develop in a new environment is the system that tracks the time spent on various projects in the information systems group This has several advantages First, it is relatively simple so you don't have to spend a lot of time on it Second, your fellow information systems staff will probably be a lot kinder if there are performance problems or bugs than your company executives would be Finally, if the system has a lot of problems, you are not affecting the company's bottom line while you work out all the bugs It is a good place to learn some of the "how-tos" and work with issues such as performance

● Always leave yourself time for problem resolution with the environment itself I have seen setup take only a day with simple environments that have been done before with only a few vendors involved, and I've also seen setup take weeks or months for cutting-edge technology An assurance from your sales representative that everything will work is not something I would bet the project on That sales representative might be completely truthful about never having had a problem setting up the software, but he might not have tried it in an

environment like yours

● Finally, go through the database stack model and spec sheets when planning the system You have to get down

to the detail level of things—such as Windows NT 3.51 on the server with the NT 3.51 TCP/IP stack interfacing

to Version 2.2 of SQL*Net and so on Whenever possible, get evaluation copies of the software and hardware

to test before purchasing the products Another alternative might be to contact others who have the same environment that you do to figure out what worked and did not work for them It is tempting to move quickly through the planning steps to get a project going, but it can cost you a lot of troubleshooting time later if you miss some things

This list of tips could continue; however, I think that these basic suggestions should get you through most of the hurdles

Do not take this as the voice of doom I have always been able to get the database network environments I work with operational Sometimes, it was a challenge to get things set up, especially in leading-edge environments; however, things usually worked well once the process was finished

Summary

This chapter took on an ambitious project To try and describe the wide range of networking options that are available in

Oracle in the space of a single chapter is somewhat like trying to summarize War and Peace in a single paragraph The

technical details of the various Oracle products fill up many different books in their manual set with detailed

configuration options and installations instructions Obviously, with the wide range of products that Oracle provides and the number of different environments it supports, I could not even begin to look at all the options here Instead, I chose

to focus on providing an overview of database networking The goal was to give you a feel for all the products that have

to work together for that seemingly simple connection from your desktop to the database

Along the way, I tried to provide some examples and share some of my experiences This is a tough chapter to come up with detailed examples (the list of configuration options that I had to set on just one configuration would probably fill a chapter in itself) I did try to summarize some of the more common tricks that I have used in the section "Network Development Tips." As a final note, I urge you to consider giving yourself an adequate amount of time when setting up a networked database environment It is easy to think that because everything is vendor-provided, all you have to do is open the boxes, load the software, and begin working I found that it often takes days to get the settings of new drivers right and get all the kinks worked out of the architecture Of course, if you already have dozens of similar installations and you are simply copying a working configuration, you might be able to get working right away On the other hand, if you have a slightly (and I mean slightly) different configuration, you should leave yourself some time for testing and problem solving

Previous

Page TOC

Next Page Home

Please purchase PDF Split-Merge on www.verypdf.com to remove this watermark.

Previous

Page TOC

Next Page Home

● 54

❍ Oracle PowerBrowser

■ What is the World Wide Web

■ Short History of the Web

■ Birth of the Browsers

■ Future Vision of the Web

■ On the Internet

■ Internal to Corporate Networks

■ PowerBrowser

■ What Is It?

■ PowerBrowser as a Web Browser

■ PowerBrowser as a Web Design Layout Tool

■ PowerBrowser as a Web Server

■ Hardware Requirements

■ Software Requirements

■ Installation

■ Navigating with PowerBrowser

■ Overview of the PowerBrowser Browser

■ Going to Your Favorite Web Page

■ Viewing Multiple Web Sites at the Same Time

■ How to Create and Use Bookmarks

■ The History List

■ Navigating within PowerBrowser

■ Sending E-Mail Using the Browser

■ Customizing the Environment

■ Setting the User Preferences

■ Setting the Cache Preferences

■ Setting the Helpers Preferences

■ Setting the Timeouts Preferences

■ Where to Go for Help

■ Designing Web Pages

■ The Hard Way: with HTML

■ Using the PowerBrowser Design Tool

■ Using the Layout Wizards

■ DBML Extension Overview

■ PowerBrowser as a Server

■ Summary

54

Oracle PowerBrowser

This chapter is about Oracle Corporation's latest Internet product, Oracle PowerBrowser At the time of this writing PowerBrowser is a beta product and may have some functionality changes However, the information here will give you

a glimpse of Oracle Corporation's plans for this product, its basic functionality, and an idea of how to use it

What is the World Wide Web

Before going into the details of Oracle's PowerBrowser, it is important to get an understanding of what the World Wide Web (a.k.a the Web or WWW) is and how it came to be First will be a short history of the Web, including the Internet, and then a description how the browser came to be Rounding out this section will be an attempt to predict what is happening with the Web and where it will take us

Short History of the Web

In the 1960s the United States government, through the efforts of the Advanced Research Projects Agency (ARPA), felt

it would be important to link university computers and researchers to assist them in conducting basic research through the sharing of information This project became known as the ARPAnet Although only 107 hosts were added to the system between 1969 and 1977, the engineers in charge of the ARPAnet realized that the new communications network was going to grow into something larger than originally anticipated On January 1, 1983, all of the ARPAnet was

switched from NCP (with a possible of 256 hosts) to TCP/IP (with a possible of 4,294,967,296 hosts) and became what

is now known as the Internet The National Science Foundation (NSF) funded most of the early development of the Internet, but on April 30, 1995, the U.S government released the Internet to commercial networks and service providers and shut down the National Science Foundation (NSF) backbone

Before the World Wide Web, the Internet consisted mostly of electronic mail (e-mail), Usenet newsgroups, and FTP or file transfer sites Tools were invented to help categorize what information could be found and where it was, but the Internet was not what you would call "user friendly." If you wanted to send e-mail to a close friend at another Internet site, the easiest way to get his or her e-mail address was to use the phone and call him or her directly (this may still be the case) If you needed a particular computer program or file, it was nearly impossible to find unless you knew exactly where it was

In March, 1989, Tim Berners-Lee at the European Laboratory for Particle Physics (CERN) proposed a new set of

protocols for Internet information distribution This set of protocols became known as the World Wide Web protocols and were soon adopted by other organizations A consortium of organizations was formed, and it became known as the W3 Consortium

Birth of the Browsers

Soon after the WWW protocols were defined, the National Center for Supercomputing Applictions (NCSA) worked on creating an interface for them The goal of the interface was to provide a graphical, easy-to-use application that would encourage others to develop and support the World Wide Web One thing that greatly helped this cause was that NCSA developed its front-end (Mosaic)simultaneously on three different graphical user interfaces (GUIs): the X windowing system found on UNIX, the Macintosh user interface from Apple Computers, and the Windows interface from

Microsoft Its release in 1993 has made the WWW the most popular Internet service in use today

Shortly after the release of Mosaic, James Clark and Marc Andreessen got together and formed Netscape

Communications Corporation Jim was one of the founders of the highly successful Silicon Graphics Incorporated, and Marc was one of the original authors of Mosaic Together they set out to build a better browser than Mosaic To help gain market share, they made their browser freely downloadable for people to try, thus setting the standard for other Web browsers Today almost every browser on the market, including Oracle PowerBrowser, is freely available

Please purchase PDF Split-Merge on www.verypdf.com to remove this watermark.

If the browsers are free, how does anyone make any money? In order to browse the WWW, you need to have servers sending information—and those are not free In order to take advantage of all the neat features the Netscape browser has

to offer, companies, individuals, and Web site providers must utilize the Netscape server Also, Netscape has started charging a very small fee for its browser

Another way that companies such as Microsoft are making money is through bundles Microsoft can provide you with a free browser or server that runs on Windows NT in hopes that it will sell more copies of Windows NT

Oracle Corporation hopes, of course, that after you have seen the power of PowerBrowser and how easily it interacts with the Oracle Relational Database Management System (RDBMS,) you will become interested in purchasing Oracle databases

Future Vision of the Web

The World Wide Web is about sharing information but is still in its infancy As more companies compete in the tools and -applications business, you will see many neat and interesting enhancements made You will also see some creative applications and uses for these products Although only time will tell what really happens, here is where the future trends in Web technology seem to be heading both on the Internet and on standalone corporate networks

WWW-On the Internet

Going through the Los Angeles Times, it is not uncommon to see WWW addresses of the companies promoting products

in advertisements Whether you are looking for computer-related products or designer clothes, you can go to the Web to see information about the companies selling you those products and information about the products themselves Soon, if you are happy with the products advertised, you will be able to purchase them through electronic means This will allow you to purchase a Hong Kong tailored suit at the local Hong Kong price without having to leave Provo, Utah or

wherever you may be

In addition to electronic commerce, you will be able to perform routine errands without having to leave your home Several banks just announced that they are setting up banking services on the WWW No longer will it require a trip to the bank to find out why your account balance is lower than your records indicate Soon, you will be able to renew your drivers license, sign up for community events, watch first-run movies, and maybe even vote via the World Wide Web One of the key technologies that will make this happen is coupling mature databases, such as the Oracle Relational Database Management System (RDBMS) with Web servers Managing these large amounts of data using current

methods is just impossible

In order for commerce to be completely enabled on the Web, vendors need to be able to perform secure transactions Although Netscape supposedly has the ability to perform secure or encrypted transactions, two computer science

students at the University of California, Berkely were able to crack the encryption method After learning of the

problem, Netscape Communications, Inc., immediately posted a new version of software that fixed the flaw the students used to crack the encryption method Although many users still feel safe using the system, not everyone will feel good about doing financial transactions over the Web until they can be completely sure about the security of their transactions

When completely secure transactions are possible on the Internet, a reliable method of storing those transactions will be necessary Currently those transactions are stored in relational databases Rather than trying to recreate technology, companies will simply couple their Web applications with their RDBMS, as has already started happening

Internal to Corporate Networks

Although I believe that it will take some time before the WWW evolves much past a larger version of what the online service providers currently have to offer, I do see some interesting things happening inside of corporations

When I ran my own consulting company, I was in the business of putting together client/server applications I generally

worked with the smaller companies that did not have the means of investing in mainframe technology With client/server computing, you leverage the desktop computer with the power of a smaller-than-mainframe-back-end-server This is a great idea on paper as far as capital costs, but it is much more complex than the mainframe solution Not only do you have to worry about application programming, you also have to worry about keeping two machines running rather than one, middleware that doesn't like your application or your network, early software that is so full of bugs it crawls, and so

on

I see Web technology replacing client/server computing in the very near future Rather than having to worry about software on the client machine, simply install a Web browser Rather than having to worry about middleware, just make sure the client and the server are running TCP/IP (the standard protocol on the Internet) Programming is reduced to writing HTML (which is discussed later in this chapter), often touted as being easier than any other computer language

In order for this to happen, Web browsers and servers are going to have to be able to talk to corporate databases such as Oracle, Sybase, Informix, or DB2 Although HTML is easy to learn, the need to talk to databases is going to mean extensions Those extensions are going to need rapid application-development tools to facilitate building Web

applications

Browsers are also going to have to be able to do some of the data validation on the client machine rather than just on the server Right now if you want to fill in a questionnaire on the Web, you do so and then press a Submit button This sends all of the information back to the server for validation If the server encounters an error, it sends the browser to a new page mentioning that it encountered an error Enabling the browser to perform validation functions will streamline the user interface, allowing client/server-type applications to be developed

Now that you have an idea of what the World Wide Web is, let's take a look at PowerBrowser and how it can help you in your quest to become Web enabled

database access, the addition of a BASIC scripting language, integration with the desktop using OLE, the ability of the browser to perform validation, and integration with the server-storing legacy data

The way the current version works is that one program handles all three tasks (browsing, designing, and serving) When PowerBrowser is officially released, it is likely to be three separately executable programs, with the design and layout tool not officially being distributed Oracle Corporation may ship an alpha version of it, then quickly follow it up with a more stable version

PowerBrowser as a Web Browser

Please purchase PDF Split-Merge on www.verypdf.com to remove this watermark.

PowerBrowser is currently a Netscape 1.1-compatible browser That means that all of the Netscape enhancements supported in version 1.1 are also supported by PowerBrowser It also supports several new enhancements such as the database mark-up language (DBML) and Network Loadable Objects (NLO), which allow enhancements to be made to the browser dynamically

Oracle is aggressively pursuing home-video-on-demand technology and has thus added the ability to play

MPEG-decoded movies embedded within an HTML page Due to bandwidth limitations, compression technology has not yet made this reliable over the Internet, but it is possible over standard Ethernet—which most corporate networks run on

PowerBrowser is a product currently under active development; by the time you read this, there will probably be several other enhancements The best place to go for up-to-date information about the browser is Oracle Corporation's Web site

at http://www.oracle.com

PowerBrowser as a Web Design Layout Tool

When you first start learning to create HTML pages (covered shortly), it seems relatively easy and straightforward—but

it is a whole lot like being blind and driving a car by feeling the bumps in the road In order to see what you have

created, you have to load the file into your browser By using PowerBrowser's designer, you can see the HTML

document as it is created

PowerBrowser as a Web Server

Creating a bunch of HTML pages is not enough to set up a Web server After the pages are created, you need some sort

of program that forwards those pages when browsers ask for them Most servers run on UNIX machines However, sometimes there may only be one or two requests a day for a particular page Rather than dedicate an expensive and difficult-to-maintain UNIX machine, you can use PowerBrowser running under Microsoft Windows (3.1 or 95)

If you are using dial-up access, you will need a copy of serial line Internet protocol (SLIP) or point-to-point protocol (PPP) If you are using online services such as CompuServe or America On-Line, they generally include such programs

with their browsers

Installation

Installing PowerBrowser is a fairly simple process If you are downloading it from the Internet, you currently have the option of saving the files on your hard disk, creating a single 1.44 MB disk or two 720 KB diskettes (as the program gets larger, more disks may be required) When you are downloading to two disks, you are prompted for the second disk

After you have the installation disk (or disks), installation is as simple as running the self-extracting executable found on the disk It asks you for the destination directory, then sets up a program group for you automatically

The hardest part about installation is actually getting the TCP/IP software installed correctly If you are sure that your networking software works fine, then PowerBrowser should not have any problems If you do have problems, the best place to go for help is: http://www.oracle.com Unfortunately, this assumes that you have a Web and an Internet

connection You can also send e-mail to torgo@us.oracle.com

After the software is installed, you need to configure your preferences This is done by going into the Options menu and selecting the Preferences option The first time you run this menu option, a Setup Wizard prompts you for information You are given the chance of doing a Generic setup, an Oracle employee setup, or Portal Information Network Setup Unless you are an Oracle employee, I suggest selecting the Generic setup You are then prompted for your userid, your full name, and your e-mail address After you fill in those fields, click on the OK button

The next time you go into the preferences, you will notice that there is no Setup Wizard and that most of the preference options are filled in

Navigating with PowerBrowser

The first thing you are going to want to do with PowerBrowser is surf the World Wide Web After you play around a bit, you will want to customize your environment so that you can find your favorite Web addresses quickly The purpose of this section is to explain that and then show you what else PowerBrowser can do as a browser

Overview of the PowerBrowser Browser

Figure 54.1 shows the PowerBrowser browser looking at my newly created skiing home page Notice how it looks slightly different than other browsers you may have seen On the left side of the screen, you notice an area containing bookmarks and an area containing a history of the places you have visited Because you can have more than one Web site open at a given time, Web sites are presented in their own child windows

Figure 54.1 The Oracle PowerBrowser browser

Going to Your Favorite Web Page

If you have not set up a bookmark with your own favorite Web site, you can specify the uniform resource locator (URL) address on the URL line shown in Figure 54.2

Figure 54.2 Specify the URL (uniform resource locator) address on the URL line to have PowerBrowser take you there

After you have entered the correct address, either press Enter or click on the GoTo button To tell you that

PowerBrowser is actually transferring data, the Oracle logo in the upper-right part of the screen rotates If the address

Please purchase PDF Split-Merge on www.verypdf.com to remove this watermark.

cannot be found, an error message appears

Viewing Multiple Web Sites at the Same Time

As mentioned above, you have the option of opening multiple web sites at the same time This can be done one of two ways The first and easiest way is to click on the New button found next to the GoTo button on the URL line This will open a new browser child window You can then enter a new URL address in the new window and be in two places at once as shown in figure 54.3

Figure 54.3 PowerBrowser allows you to see two Web sites at the same time

How to Create and Use Bookmarks

The World Wide Web is a big place full of all sorts of interesting sites When you are surfing the Web it is nice to be able to get back to your favorite sites without having to remember the URL addresses (trust me when I say they are easy

to forget) Figure 54.4 shows the bookmark section in PowerBrowser

Figure 54.4 Here are some of the bookmarks that come with PowerBrowser

Notice how bookmarks are stored in separate books or bookmark folders Rather than list all of your bookmarks

together, you have the ability to classify them into separate categories This makes it easier to find Remember the Web

is a big place and you may have hundreds of favorite sites, not just a handful

To add a folder use the Add Folder menu option of the Bookmarks menu You are presented with the dialog box shown

in Figure 54.5 Provide the name of the folder that you would like to create If you check Add as child of selected folder, the new folder will be inside the currently selected folder This enables you to have folders containing other folders Once you have given the folder a name, click on the OK button

Figure 54.5 The dialog box used to create new bookmark folders

To add a bookmark to the currently selected folder, use the Add Bookmark menu option in the Bookmarks menu The Edit Bookmark Details dialog box shown in Figure 54.6 should appear

Figure 54.6 The dialog box used to create new bookmarks

Unlike adding a bookmark folder, adding a bookmark is slightly more involved You are allowed to specify the name of the bookmark, which will appear in the bookmark subwindow on the left of your screen Next, specify the URL address

I suggest making sure the URL address is valid by copying it from the URL line in the browser using CTL+C before opening the bookmark dialog box and then pasting it in the bookmark dialog box using CTL+V Should you require it, you can specify the protocol and any extra parameters

In the current version, it is important to use the Save Bookmarks option in the Bookmarks menu before exiting

PowerBrowser Otherwise, the bookmarks created during your session will be forgotten

After you start using bookmarks extensively, you are going to want to do more than just add them Editing and Deleting bookmarks and bookmark folders can all be done through the Bookmarks menu

Should you be migrating from Netscape and want to take all of your existing bookmarks with you, PowerBrowser has an

option to migrate them; this obviates the need for you to recreate them Simply select the Import Bookmarks option from the Bookmarks menu; this brings up a file dialog box, from which you can choose the file that contains your current Netscape bookmarks

The History List

During any PowerBrowser browsing session, you may come across one or two sites that merit going back to If you will

be going back continually, it is best to create a bookmark However, if you will only be going back once or twice, it is better to use the history list as shown in Figure 54.7

Figure 54.7 Use the history list shown here to go back to recently visited Web sites

Unlike bookmarks, you do not need to manually add items to this list PowerBrowser automatically keeps track of the Web pages you have recently accessed and lists them by page header on the left of your screen To go back to a recently visited page, simply double-click on the name found in your history list If the page is still in the cache or buffer, then it will load immediately Otherwise, it will go out and reload that page for you

After you are done with your history list, you have the option of clearing it out using the Clear option found on the Navigate menu

In addition to being able to use the history list to revisit recent sites, you can also use it to audit where your browser has been I am the father of three children, and naturally they like to use the Web Although they are currently quite young and would never venture into questionable Web sites, I have the option of auditing where they go without having to stand over their shoulder I make sure to clear out the history list before they start and then make sure it has a sufficient number of entries when they are done Just knowing that I can do this will hopefully keep them from learning how to make fertilizer bombs in junior high

Navigating within PowerBrowser

To help you navigate the Web, PowerBrowser has several options found on the toolbar as shown in Figure 54.8

Figure 54.8 The toolbar found at the top of the PowerBrowser window

If you place the cursor over a toolbar button and wait, tool tips will appear letting you know its function Notice that the first three toolbar buttons (going from left to right) have to do with which mode you are in (Browser, Server, or

Designer)

The next button enables you to load an HTML page from your disk This is great for testing an HTML page that you have created before placing it on a server Following this button is the one that takes you to your favorite home page I'm

an Oracle fan, so mine naturally points to the Oracle Web page

The next group of two buttons enables you to go forward or backward If you have been navigating through the Web and need some information from a previous page, use the back arrow to go back to it After you have the information, use the forward arrow to go ahead to where you were before you went back The arrows should be grayed out or disabled when there are no pages to go back or forward to

The buttons following are used to reload a page or go back a whole level Because I access the Web using dial-up lines, there is sometimes garbage on the line and large graphics may be garbled When this happens I simply reload the page, and most of the time it comes through clean the second time

Please purchase PDF Split-Merge on www.verypdf.com to remove this watermark.

Next is the Stop button When loading a large HTML page or graphic, it is nice to be able to stop it using this button

The last three buttons on the toolbar are used to copy, print, and get help When you come across needed information in

a Web page, it is nice to be able to print it out

Sending E-Mail Using the Browser

When browsing the Web, you often have the chance to send e-mail to administrators of Web sites PowerBrowser allows you to send mail by clicking on Send Mail option in the File menu Be sure that you have configured PowerBrowser so that there is an SMTP server, or it will complain

Customizing the Environment

I was recently at a conference with two of my coworkers, and we all had the same exact laptop computer with pretty much the same software Throughout the course of the day the laptops were continually being used, and it was amazing that, although one laptop may have been closer, each of us preferred to use our own Why? Because each of us had configured our laptops to our liking Although the developers of PowerBrowser have come up with some nice User Interface features, not everybody will like them It is nice to be able to configure PowerBrowser to your own liking

Configuring PowerBrowser is fairly straightforward The first configuration that you are going to want to do is making sure that all of your preferences are set up correctly This can be done by going into the Preferences option of the

Options menu It will then bring up the Preferences dialog box shown in Figure 54.9

Figure 54.9 The Preferences dialog box allows you to change certain preferences

Notice the tabs across the top Five separate categories are listed: Proxies, User, Cache, Helpers, and Time-outs When filling in the information for Proxies, it is best to talk to your system administrator to find out which values should be used If you are the system administrator and don't know which values should be here, initially leaving them blank is probably the best thing to do After you become more familiar with the Web and your network, it will become apparent which values you should use

Setting the User Preferences

When installing PowerBrowser for the first time, you should have entered some of the basic user preferences Figure 54.10 shows the user preference specification dialog

Figure 54.10 This is where you specify user preferences for PowerBrowser

The User ID, Full Name, and E-mail address should already be filled in If you need to change any of this information, this is the place to do it The Reply-To line allows you to specify a second E-mail address, should you want replies to your original to go someplace other than your original E-mail address When it is left blank, the Reply-To defaults to your previously specified E-mail address

PowerBrowser has used the default options for the rest of the user preferences, but you may change them in this dialog

The Start with preferences determine what happens when PowerBrowser is initially started The default is to not go to any page on the Web The other option is to automatically load your home page For those directly connected to the corporate network or the Internet, this is not a bad option For those using dial-up lines (like me), it is nice to not have it connect to the home page immediately Notice how there is a line where you can dynamically set your home page location

The next set of options specifies the overall look of the HTML pages while you are looking at them Notice that you have the option of looking at images while they are loading or only after they are done You also have the option of changing your proportional and your fixed-width fonts When you click on either of the buttons, the Windows font dialog appears listing all of the fonts you have on your system This requires that you load the desired fonts onto your system before you can use them in PowerBrowser

The next three, and final, options specify color settings You have the option of dithering colors to match those in your color palette or just choosing the closest on the palette The default is to dither, and I recommend this setting Finally, you have the option to disable the palette control for images

Setting the Cache Preferences

In the first half of 1995, the Client/Server Systems Division (now renamed the Web/Workgroup Systems Division) was responsible for putting on seminars throughout the United States During the seminar, we demonstrated that you could use the Web to download trial versions of our software Unfortunately we could not be guaranteed direct Internet

connections at any of the seminar sites This meant that we were required to use dial-up lines, and graphical images were drawn unbearably slowly To keep the presentation interesting, the technical person responsible for the seminar would log onto the Net and run through all of the HTML pages that would be demonstrated before the presentation began This had the effect of caching all of the images so that during the presentation, they were never downloaded Unless you are doing something similar, you will probably never worry about the cache parameters in PowerBrowser

The cache preferences screen is shown in Figure 54.11 The defaults should suffice for most users

Figure 54.11 The PowerBrowser cache preferences or parameters

The first preference actually tells where the home directory for PowerBrowser is Unless you manually move files around on your hard disk after installing PowerBrowser, you should not have to change this parameter

In the cache preferences, you have the ability to specify the cache directory, and how large it is A one-megabyte cache should be large enough for most users If you are frequently going between large pages with lots of graphics on each page and don't want to reload pages all the time, then you may want to increase the size to something larger When we were doing the seminars program, eight megabytes was more than enough

Next you have to option of specifying how often to reload pages and whether or not to temporarily disable the cache The only time I have ever disabled the cache is when doing performance analysis on my own local network Sometimes you want to get an average of how long it takes to load several pages, and so it is nice to be able to manually disable the cache When browsing the Web for information, however, you will rarely have the need to turn it off

Finally, you have the option of clearing out your cache immediately

For most users, the cache preferences will rarely be altered If you do need them changed, however, this is the area to do

it

Setting the Helpers Preferences

The Web is a dynamic place, making things possible today that weren't even thought about yesterday Today it is

common to see bit maps and text at most Web sites; tomorrow we will be seeing video and animation In order to see this new media, PowerBrowser has the ability to specify helper applications

Helper applications make it possible to process media types that are not currently built into PowerBrowser For instance, some browsers cannot natively display JPEG files To get around this limitation, these browsers utilize a helper

Please purchase PDF Split-Merge on www.verypdf.com to remove this watermark.