Oracle Unleashed- P6

Connected to: Oracle7 Server Release 7.1.4.1.0 - Production Release With the distributed and parallel query options PL/SQL Release 2.1.4.0.0 - Production Import file: ./expdat.dmp > scot

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Enter table name or if done: dept

Enter table name or if done:

The last example is from full database mode

Import entire export file (yes/no): yes >Y

User Mode

The user method of Import enables you to import tables that belong to a specific user This can also be combined with the table mode to import specific tables from a specific schema This is important because Import attempts to create the tables in the current schema's default tablespace if the schema specified in the export file does not exist This can work to your advantage if you need to move tables from one schema to another

Table Mode

You usually use table mode to import a table or a list of tables, rather than all tables in the export file If a user has access

to other schema, he can import tables from other schema by qualifying with the schema name The default is to import all tables in the schema of the user doing the import

Full Database Mode

The full database option of Import does not quite work the same way as the full database option of Export If you specify the full database option in Export, the entire database is exported, and to import the entire file, you must have the role IMP_FULL_DATABASE assigned to you If the export file is a user export or table export, the entire export file is imported (whatever is in it), and you do not need to have the role IMP_FULL_DATABASE assigned to you

Interactive Versus Command Line

Both Import and Export can operate in command-line mode and in interactive mode Both modes have their advantages, but Oracle recommends that you use the command-line mode with a parameter file The two modes are outlined in this section I'm sure you will find good reasons for using both in your own situation

Interactive Method

The interactive method is an easy way to import data from export files, but you do not have all the options of the

parameter or command-line method For example, you cannot create an index file The interactive prompts might change depending on the response to previous prompts The interactive prompts also have the benefit of showing the prechosen

defaults To use Import in the interactive mode, type imp or imp USERID=userid/password at the command line

The interactive method continues to exist only for backward compatibility

An interactive import might resemble the following:

/usr/local/p3016dk > imp scott/tiger

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Import: Release 7.1.4.1.0 - Production on Sun Oct 1 10:12:54 1995

Connected to: Oracle7 Server Release 7.1.4.1.0 - Production Release

With the distributed and parallel query options

PL/SQL Release 2.1.4.0.0 - Production

Import file: /expdat.dmp > scott.dmp

Enter insert buffer size (minimum is 4096) 30720>

Export file created by EXPORT:V07.01.04

List contents of import file only (yes/no): no >

Ignore create error due to object existence (yes/no): yes > n

Import grants (yes/no): yes > y

Import table data (yes/no): yes > y

Import entire export file (yes/no): yes > y

Command-Line Method

The same import can be accomplished by entering the following command-line options

imp USERID=scott/tiger FILE=scott.dmp ignore=N

Import responds with the following:

Import: Release 7.1.4.1.0 - Production on Sun Oct 1 10:19:12 1995

Connected to: Oracle7 Server Release 7.1.4.1.0 - Production Release

With the distributed and parallel query options

PL/SQL Release 2.1.4.0.0 - Production

Export file created by EXPORT:V07.01.04

importing SCOTT's objects into SCOTT

importing table "BONUS" 0 rows imported importing table "CUSTOMER" 9 rows imported importing table "DEPT" 4 rows imported importing table "DUMMY" 1 rows imported

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importing table "EMP" 14 rows imported importing table "EXECUTABLES" 0 rows imported importing table "FALL5" 30 rows imported importing table "ITEM" 64 rows imported importing table "ORD" 21 rows imported importing table "PRICE" 17 rows importedImport terminated successfully without warnings.

Import Parameters That Affect Performance

As with Export, Import also has several parameters that affect performance This section lists the parameters that affect performance the most along with an explanation of how they work and how to use them

LOG

Quite simply, always use the LOG parameter so you can review the log file and effectively fix anything that went wrong

How Objects Import

Objects are created in a specific order as the import progresses The important thing to remember is that Import first creates the table and then loads the data for each table Import creates all the indexes on the tables after it loads all the table data Finally, Import enables all the table constraints and triggers In some situations, the table constraints can cause interesting results (usually undesirable) If you are in the habit of precreating the tables before the import as I am, you know you'd better disable the constraints before importing Reenable the constraints when the import is finished Don't forget!

Tables

Import first creates the table definitions and then loads the data Import creates all the indexes for the table and then creates and enables the constraints and database triggers The important thing to note is that all the tables are loaded and all of the indexes are created a table at a time When the tables are finished, Import creates and reenables all the table constraints

Stored Procedures

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Packages, functions, and stored procedures are imported without updating the time stamp This enables Oracle to use the objects without recompiling them

Snapshots

Snapshots are exported quite uneventfully Oracle exports and imports the master table, the master table trigger, the snapshot log (if you are using one), and the snapshot itself, similar to exporting and importing tables and database triggers If you are using a snapshot log, only the snapshot log definition is exported and imported What this means to you is that the first fast refresh that is attempted on that snapshot will fail Plan on a complete refresh of all of the

imported snapshots after the import is complete

Importing and Exporting with Personal Oracle7

My world has not been the same since Oracle introduced Personal Oracle7 I have been able to develop complete

applications on my PC at home Although I do not have a PC platform that compares with our Sequent, HP, or DG platforms, I can't resist the desire to develop applications on it I haven't yet used Personal Oracle7 for any production applications, but I am sure many people have

All of us who have had the pleasure of experiencing Personal Oracle7 will agree that the Windows front end on the Import and Export utilities is a nice addition to the old familiar utilities I think that many Personal Oracle7 users like me are developing applications I find myself exporting tables from the true development platforms at the job site and then importing them into my PC database so I can develop whenever and whatever I like

Using the Personal Oracle7 version of Import and Export is quite a bit different from the old standards Personal Oracle7 has a nice GUI interface that is hard to beat It still works internally the same way as the character versions and outputs files that you can transfer to other Oracle instances The main difference in Personal Oracle7 is the Windows front end Figure 9.1 shows the Export utility in Personal Oracle7; the title bar has the caption Database Exporter The first thing you notice is that parameters are represented by text boxes, checkboxes, or pull-down lists Figure 9.2 shows the

advanced options The advanced options are Record Length (RECORDLENGTH), Buffer Size (BUFFER), Record Export in System Data (RECORD), Keep Components Consistent (CONSISTENT), Compress When Imported

(COMPRESS), Log File (LOG) Increment Type (INCTYPE), and Statistics Type (STATISTICS) The other Export parameters follow similar translations

Figure 9.1 Personal Oracle's Export utility.

Figure 9.2 Export utility advanced options.

Figure 9.3 and 9.4 show the Database Importer and the advanced options available The Database Importer closely resembles the Exporter's look and feel I do not go into detail because its functionality is fairly obvious

Figure 9.3 The Import utility.

Figure 9.4 Import utility advanced options.

Import and Export Hints and Tips

You can use Import and Export for tasks other than just backing up data I often use Import and Export for several other constructive reasons, and this section outlines a few of the best hints and tips

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Create an Index File

Import can create what is known as an index file This is a SQL script of not only the creation scripts for the indexes in the export file but also creation scripts for the other database objects in the export file All the lines in the file except for the index creation scripts are commented out The commented-out code contains creation scripts for the remaining objects in the export file With some editing, you can create a script that can be used to precreate all the tables and indexes and so on This is often necessary if you use the parameter COMPRESS=Y

Adjusting Storage Parameters

Using the parameter COMPRESS=Y rewrites the original storage parameters so that the table or index resides on one contiguous extent Compressing the extents is a good idea as long as you actually have the contiguous extents available

I suggest precreating the tables and indexes with your edited INDEXFILE This ensures that you can actually create the objects Of course, if any table or index fails to create, you can adjust the initial and next extents in the INDEXFILE and attempt to create the table again This is also a good time to adjust the PCTFREE and PCTUSED and the

TABLESPACE parameters (or any of the other table parameters) in the table and index creation statements I highly recommend that you study and adjust the size requirement if necessary at this time, especially if the storage parameters are set to their defaults I don't go into great detail, but here are some good places to start if you have a mess of default storage parameters:

Parameter Defaults to Set to

25% up to the size of INITIAL

There are other storage parameters, but these five are typically the most important to me

Reorganizing Data

Users own tables, indexes, and other objects The tables and indexes users create reside in tablespaces If you were to export a user's tables, drop them, and then import them, they end up in the user's default tablespace again If you need to move tables from one tablespace to another, you export the tables and change the user's default tablespace and quotas to another tablespace that you want to contain the tables Then, when you reimport the tables, they are created in the new default tablespace

Reducing Database Fragmentation

When a database has many small blocks of free space, you should export it with the FULL=Y parameter Recreate the database and then do a full database import Tablespaces also need similar help You should plan carefully where and how many data files a tablespace has To recreate the tablespace, export all the objects, using the nifty script I provided if Please purchase PDF Split-Merge on www.verypdf.com to remove this watermark.

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you like Drop the tablespace including its contents Recreate the tablespace and then import the fresh new tablespace

Migrating from Version 6 to Oracle7

Import can read export files from Version 6 Oracle You could use this function to migrate by exporting the Version 6 database and then recreating the database in Oracle7 Some data type changes occurred after Version 6; the old Version 6 CHAR data type changed to VARCHAR2 Import handles this conversion for you If you're wondering who is going to change all your table creation scripts from the old CHAR data type to VARCHAR2, try using the INDEXFILE

parameter explained earlier Oracle7 provides vastly expanded integrity constraints, and the SQL syntax is slightly different from Version 6 All the existing constraints are exported, but only the NOT NULL constraint is imported and enabled

Importing Tables with LONG and LONG RAW Data Types

Did you know it is possible to export a table with extremely large columns (LONG data types can be up to 2 GB in length) only to discover that they cannot be imported? It hasn't happened to me, but Oracle reports that this could

happen The reason is that Export can break up the long data, but Import must read the data into contiguous memory to import If you do not have enough memory, the import fails

Summary

Import and Export not only provide data recovery, but they have quite a few database management uses as well I am sure you will find yourself using Import and Export often to keep your database tuned well by reducing fragmentation and enabling yourself to change the storage parameters of tables and their locations or owners Whatever task you choose for Import and Export, you will find them to be a stable pair of utilities that are easy to use

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■ Parallel Server Option

■ Parallel Query Option

your operating system can be found in the Oracle Installation and User's Guide manual which comes with the software

In addition, the last-minute System Release Bulletin that comes with the software should be studied, along with the even

later produced README.DOC file that is on the install media

On most platforms, if a user process connects directly to the database server machine, two things must be known One is the starting location of the Oracle software directory, and the other is the instance identifier to which the user process will connect to This information is provided in different ways on different operating systems, but many use an operating system command file named something such as "orauser" or "oraenv" to set up these operating system variables as soon

as a user logs into the machine

During the installation process, on most machines, an option is given to install a default database by choosing some menu options Chapter 11, "Managing the Database," covers how to create a database if you either don't want to or can not use the menus to give you this starting database Usually the menus are sufficient to create a practice database, but for production and real systems, more control is needed over the choices available when creating a new database

Installation of the Oracle tools is usually done at the same time as installation of the Oracle software For client/server environments, an added complication is that the tools exist on a different machine than that on which the database software resides To allow the two machines to communicate between each other, some networking software must be installed on both machines (such as TCP/IP), and on top of that both machines need a flavor of SQL*Net installed so that the Oracle software can interface to the networking software Installing SQL*Net software for the network protocol you're using is usually done at the same time as installing the Oracle server software and tools software

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This is one of the areas where there are major differences between different operating systems due to the nature of the process itself

Oracle Software Options

When you purchase the Oracle software, a number of additional software options are available However, these options may not be available on all platforms at the same time (for example, at the time of this writing, the Distributed option was not yet available on the Personal Oracle 7 version of the software)

Base Product

The standard product (without the addition of the procedural, distributed, parallel, or other options) gives you the SQL language—without this not much can be done on the database In the near future, the PL/SQL language is also to be included in the standard, base product In addition, the database only locks those rows which are actually being modified instead of locking out the entire table (This was an option that had to be purchased separately in version 6 of the

database server.)

The base product also includes the capability to do parallel recoveries in the case of media failure, which means that you can have more than one process running the recover tablespace command All of these processes can run in parallel and will use whichever archived and online redo log files are required for the tablespace being recovered Parallel tablespace backup commands can also be issued, as well as parallel loads of data from operating system files using the SQL*Loader product with the direct load path option, which is available with that product

Procedural Option

The procedural option gives the you ability to use PL/SQL and to create procedures, functions, packages, and database triggers At the time of this writing, this was being bundled in as part of the base product, and so was not an additional option for most platforms

Distributed Option

The base product itself gives you the ability to write distributed queries—queries which in the same transaction or even

in the same statement, query tables on one or more databases, usually by using database links (which have already been defined by the database administrator) In addition, the user can connect to a remote database and make changes to tables

on that database

However, one thing that is not possible without the distributed option is the capability to make changes to tables on more than one database within the same transaction (the same commit unit) The distributed option allows one transaction to make changes to more than one database When the changes are committed (or rolled back), the Oracle server software ensures that either all the databases commit, or if anything goes wrong, that they all rollback the work This is provided without requiring the developer to put in any more code than the normal commit or rollback statement

The synchronization mechanism is provided using the 2-Phase Commit algorithm, which synchronizes all the databases involved

In addition, with the distributed option, one non-Oracle database can take part in a distributed transaction Usually this involves using the Oracle Gateway products which allow access to non-Oracle data sources

If any failures do occur with a distributed transaction, the Oracle RECO background process periodically tries to either commit or to rollback the changes on the databases involved It is better for the database administrator to allow the RECO process to recover the distributed transaction without getting involved The Oracle data dictionary tables,

DBA_2PC_NEIGHBORS and DBA_2PC_PENDING, give further information on the transactions which have been Please purchase PDF Split-Merge on www.verypdf.com to remove this watermark.

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involved in a distributed failure

The distributed option is also required if you wish to create Snapshots which are copies of tables (usually) on other databases which are automatically replicated to your database at user defined intervals In addition, the distributed option includes the capability to call procedures, functions, and packages, which have been defined on remote databases So, in theory though not very practically, you can hold the database procedures, functions, and packages on one central

database, and all other databases can make calls to this central copy of the code

Parallel Server Option

The Oracle parallel server option allows more than one instance to access the same set of database files This option ensures, for example, that if a row is locked on one instance that it is reported as locked on any other instances accessing the same database

The parallel server option is be used where more than one processor is available (either in the same machine or in

different machines which have been clustered together)

Parallel Query Option

The parallel query option improves performance of full-table scans This allows a large query to be executed by multiple processes so that many processes can be used to perform parts of the query, with the results being merged together automatically

In addition, the parallel query option allows creation of indexes in parallel This is similar in concept to the parallel query mentioned earlier, where more than one process can be used to build different parts of the index, and the results from each of these processes is merged together

The parallel query option normally runs on those machines where more than one processor has been installed so that you can use the processing power of more than one processor to perform the heavy-load work which you require

Trusted Oracle

Trusted Oracle provides additional security than what is available with the base product and is usually found either in military type applications or those where a high level of security is required This gives, for example, the ability to control which rows are accessible to which users This is not easily done with the base product

Tip: Use the v$version view, which is accessible to the system user, to see which versions of the Oracle product you have installed In addition, the v$compatseg view shows which version of the Oracle server software

introduced some of the new releases

Installation Preparation

The actual process of installing the Oracle software and creating the first database is relatively easy on most platforms because you can follow the menu options; however, preparation before the actual install pays dividends in the long run

One of the first things to consider is the amount of disk space required both for the software and for the database itself

In addition, the locations of the program files, database files, redo logs, and control files should be carefully considered

so that disk contention does not occur

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The amount of storage required for the software varies from platform to platform—the Oracle installation and User's Guide manual for your platform should be able to give you an idea for the amount of storage required

The amount of memory required for Oracle will be split into the memory required for the Oracle software to load (much

of which is re-entrant code that can be used at the same time by more than one process), the common memory areas (such as the SGA), and the private memory areas (such as the PGA for each connection to the database), as well as memory for the client programs which are executing Though, this may be on a different machine than the one on which the database server is being run

The default memory allocations (especially for the common SGA area) is not sufficient for most databases

In addition, some operating system specific issues need to be addressed (such as the number of semaphore sets in UNIX)—most of which will be detailed in the installation and user's guide manual

Installing the Software

Most platforms have a menu driven installation script or, even better, an installation program that makes the installation

a one-stop point-and-click operation, such as the program for installing the Oracle software on the Microsoft Windows platform Because dependencies exist between different components of the Oracle software, the menu first prompts for the components of software to be installed and works out the dependencies between the different components so that all required components are installed

On some platforms, it may be necessary to create an operating system account with a high-level of privileges which will

be used to install the software (usually called Oracle7)

The operations of connecting as internal, starting up the instance, shutting down the instance, and creating a database are all privileged operations They can all be performed from within the SQL*DBA tool (or from the server manager tool if that is available on your platform) As a result, your operating system account needs to have the necessary operating system privileges in order to perform these operations (UNIX groups on UNIX, or process rights on VMS, for example) The way that Oracle determines whether these privileges are in effect is different from platform to platform

At the time of this writing there is no check to ensure that you only install the products for which you are licensed, or that you do not exceed the number of users for which you've bought the license for

Use the v$license view to determine whether you are exceeding the number of users for which you're licensed

Directory Structure

For those platforms where a hierarchical directory structure exists, the Oracle default home directory has a name such as

"Oracle7," and below this you'll find many subdirectories—usually one for each product being installed Within each of these product subdirectories, further subdirectories exist for things such as the install scripts, demo files, and so on

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where to find the different files for the software being installed

For those platforms that support it, an operating system environment variable exists to define where the starting location

is for the Oracle software ($ORACLE_HOME for UNIX, ORA_ROOT for VMS and the ORACLE.INI file for the MS Windows platform) Once this environment variable exists, Oracle can work out the locations of the subdirectories and gain access to the files it requires

It is also possible on some platforms to install many different versions of the Oracle software

Operating System Specifics

In this section, we highlight some points for three of the major platforms for Oracle

UNIX

In addition to an installation and user's guide manual being provided for your platform, there is also a generic UNIX technical reference guide which applies to all UNIX platforms on which Oracle can be run This should be read in conjunction with the installation and user's guide before starting the install

The $ORACLE_HOME environment variable is used to locate the home directory for the Oracle software, and the

$ORACLE_SID environment variable is used to determine which instance ID the user process will connect into

The PATH environment variable should include the $ORACLE_HOME/bin directory so that you can access the various Oracle components

One of the options available for the UNIX platform is to allow Oracle to use raw disk devices—essentially this means that the Oracle software can bypass the buffer manager for the disks and access the disk drives directly giving an increase in performance However, you should ensure that the necessary UNIX expertise is on-hand to manage raw disk devices—something that is not to be considered for those sites new to UNIX and new to Oracle

VMS

The ORA_ROOT logical is used to point to the location of the home directory for the Oracle software In addition, the ORA_SID symbol is used to determine the instance identifier of the instance to which user processes will connect

MS Windows

This is nowadays one of the easiest platforms on which to install the Oracle tools and software

The ORACLE.INI file is used to set the various parameters used by Oracle The parameters ending with path control where the Oracle software on the PC attempts to find the Oracle software The default location of the database server machine, the network protocol used to connect that machine, and the instance identifier used when a connection is made

to that machine, can be given by the LOCAL parameter in the INIT.ORA file

Summary

In this chapter, you have seen an overview of some of the things to consider when installing the Oracle software This is one of the areas where major differences exist between different platforms As mentioned earlier, you refer to the installation and user's guide manual for your platform to learn the specifics for your platform

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● 11

❍ Managing the Database

■ The Parameter File: INIT.ORA

■ The Oracle SID

■ Creating a New Database

■ The First Objects Created

■ Startup and Shutdown

■ Startup Stages

■ Shutdown Stages

■ The Data Dictionary

■ Core System Tables

■ Data Dictionary Views

■ Dynamic Performance Tables

■ Other Data Dictionary Views

■ Redo Logs

■ Creating, Altering, and Dropping Redo Logs

■ Multiplexing Redo Logs

■ Control Files

■ Multiplexing Control Files

■ Trace and Alert Files

■ Database Modes

■ NOARCHIVELOG Mode

■ ARCHIVELOG Mode

■ Changing the Mode of the Database

■ Useful Data Dictionary Views

■ Summary

11

Managing the Database

In this chapter, you learn how to perform the following tasks:

● Make a new Oracle database

● Manage the instance by bringing the instance up and down

● Obtain information from the Oracle system tables

● Modify the number of control and redo log files

The Parameter File: INIT.ORA

An instance is the set of background processes and the memory structures that Oracle uses Every instance must have a parameter file, known as the INIT.ORA file, from which it retrieves the parameters that it uses to run and the mode of Please purchase PDF Split-Merge on www.verypdf.com to remove this watermark.

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the database This parameter file is used by the Oracle SQL*DBA tool when the instance is first started Once the

instance has been started, the parameter file is not used again until the next time the instance is started The parameter file must be on the same machine as the SQL*DBA tool

INIT.ORA parameter files are used to specify

● Amount of storage allocated for the Oracle memory structures

● Which rollback segments to use for the instance

● National language settings

● Settings for running Oracle in parallel server mode

● Which database and control file to use

● When to issue checkpoints

● Limits for database control structures

● Which non-mandatory background processes to initialize

The file is given the generic name INIT.ORA, but the Oracle instance identifier is usually part of the filename The name can be any filename, but it usually begins with INIT

The parameter file is an ordinary text file, which you modify using any character-based operating system text editor The parameters can be included in any order, and they can be specified in upper, lower, or mixed case

Even though the parameters can be included in mixed case, the names of operating system files must be specified according to the operating system's rules for file naming In UNIX, for example, a filename must be specified exactly as

it appears on the file system

You specify over 130 parameters Most of them are common to all the platforms on which Oracle runs The number of the parameters increase from one release of the Oracle RDBMS software to the next

An example parameter file comes with the Oracle software; its default name is INIT.ORA You can use this file could to run your instance, although you might have to adjust the parameters manually to obtain optimal performance

It is possible to many parameter files for the same instance, although only one is used at a time for the instance startup If you want to use another set of parameters for the run, you must shut down and restart the instance

Many parameters have a minimum value If they are set below the minimum value, the Oracle instance does not start up The values of some parameters are derived from settings in other parameters Normally, you do not need to set them There are even some parameters that you should not set unless the Oracle support desk instructs you to set them

Appendix A of the Oracle7 Server Administrator's Guide describes all the different parameters

Use one parameter file for the instance for normal online operations during the day At night, use a parameter file that optimizes performance for a batch job

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In the INIT.ORA file, the only parameter that is mandatory is the CONTROL_FILES parameter, which names one or more control files to be used for the instance This control files are used during instance startup to determine the names and locations of the database and redo log files Table 11.1 describes additional parameters for the INIT.ORA file

Table 11.1 Important INIT.ORA parameters.

AUDIT_TRAIL Must be set to TRUE to enable auditing rows to be inserted, even if the auditing facility has

been set up by issuing the AUDIT SQL command

BACKGROUND

_DUMP_DEST

Controls the directory location where the trace files from the Oracle background processes are written The alert file, which records significant database events and messages, is also written to this location You can delete the trace and alert files without affecting the performance of the database

CHECKPOINT_

PROCESS

Controls whether the Oracle CKPT background process is to be run By running the CKPT process, load is decreased from the LGWR process in updating the database file headers whenever a checkpoint occurs

CONTROL_FILES Names one or more control files to be used for this instance Control files are used during

instance startup to determine the name and location of the database and redo log files

DB_BLOCK_BUFFERS Specifies the number of Oracle database blocks to cache in the database buffers area of the

SGA The default value of 32 is too small for all but test databases

DB_BLOCK_SIZE Specifies the size of each Oracle block in the database files Set this parameter when you

first create the database and then do not alter it

DML_LOCKS

Specifies the maximum number of DML locks that can be taken out by the instance There

is one DML lock for each user for each table undergoing an INSERT, UPDATE, or DELETE operation at any time for the instance

INIT_SQL_FILES

Specifies the name of the sql files to be executed when the database is created These files are typically the Oracle-supplied files used to create the data dictionary, the views on the data dictionary, and views that enable the export and import utilities to run After these files have been run during the CREATE DATABASE operation, they are never executed again

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LOG_ARCHIVE_

FORMAT

Controls the naming format of the archived files if the database is running in ARCHIVELOG mode That way, the redo log sequence number, instance thread number, or

a fixed string can be inserted into the filename

LOG_BUFFERS Specifies the size of the redo log buffer in the SGA into which all changes are recorded

from all transactions on the instance

LOG_CHECKPOINT

_TIMEOUT

Controls the amount of time to wait before issuing a checkpoint on the database For example, if this parameter is set to 1800 seconds (30 minutes), a checkpoint is performed every 30 minutes, even if no activity has occurred on the system in the period

MAX_DUMP

_FILE_SIZE

Specifies the maximum size of any trace files generated If you use the trace facility to trace large amounts of work, use this parameter to limit how much trace information can be produced

OPTIMIZER_MODE

Specifies the default mode for the Oracle optimizer, which determines the execution plan for a SQL statement The Oracle6 method is RULE, which means that the optimizer does not take account of any statistics that were gathered on tables by using the ANALYZE command The default value, CHOOSE, uses statistics if they exist Otherwise, it defaults to the rule based on the optimization method

OS_AUTHENT

_PREFIX

Specifies the proxy login The Oracle user name defaults to the operating system user name prefixed by OPS$ You can control the password by using this parameter The default on most platforms is OPS$, but you can change it to any prefix or even NULL

PROCESSES

Controls the maximum number of operating system processes that can connect to the Oracle database through this instance, which includes the background processes Four background processes are mandatory, and the instance cannot start without them

RESOURCE_LIMIT

Must be set to TRUE to enforce checking of resource limits if system resources are controlled through database profiles assigned to Oracle users To set this parameter online, use the ALTER SYSTEM command

ROLLBACK_

SEGMENTS

Contains the names of private rollback segments that the instance should use for storing the before-image of any changes made to the database Rollback segments not mentioned here can still be activated by using the ALTER ROLLBACK SEGMENT command If no rollback segments are activated, the SYSTEM rollback segment—normally reserved for recording changes made to the Oracle data dictionary—is used for recording the before-image of the Oracle data blocks If more than one instance is using the Oracle database, they cannot use the same rollback segments

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SEQUENCE_CACHE_

ENTRIES

Specifies the number of sequence objects to cache in the SGA for generating unique numbers using sequences The sequences must have been created with the CACHE parameter specified as part of the CREATE SEQUENCE statement

SHARED_POOL_SIZE Specifies the size of the shared pool area in the SGA that is used to hold the data dictionary

cache, cursors for SQL statements, and PL/SQL code units

SMALL_TABLE_

THRESHOLD

Sets the low threshold for the data blocks in an Oracle table Tables with Oracle data blocks below this limit are read into the SGA completely when you perform a full table scan on them If a table has more data blocks than this limit, the full table access of the table uses only a portion of the lower part of the database buffers cache of the SGA This ensures that active blocks in the SGA from other tables are not removed from memory when a full table scan is performed on a large table

SQL_TRACE

Turns on the trace facility for the instance when set to TRUE With tracing on, execution plans and statement performance can be determined by formatting the trace files produced with the TKPROF utility Timing information is provided only if the TIMED_STATISTICS parameter is also set to TRUE

TIMED_STATISTICS Determines whether timing information is recorded in the trace files when tracing is enabled

for the instance or for user sessions

USER_DUMP_DEST Determines the location of user process trace files produced when tracing is enabled for the

instance or for user sessions

Table 11.1 does not describe all the parameters in the INIT.ORA file Refer to Appendix A of the Oracle7 Server Administrator's Guide for descriptions of the all parameters

Use the IFILE parameter to name a file that contains a common set of parameters for all the instances running on the machine

To see the parameters that the current instance is using, enter the following in SQL*DBA:

SQLDBA> SHOW PARAMETERS

You can also see only those parameters that contain a given string For example,

SQLDBA> SHOW PARAMETERS buffer

shows all the parameters that contain the string buffer

To see a list of the parameters when the instance first comes up, include the word LIST in the first line of the INIT.ORA file

To access the parameters from any Oracle tool, run a select operation against the v$parameter table, as in

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SQLPLUS> SELECT * FROM v$parameter.

You must have access to the v$parameter table, which is owned by the Oracle user SYS

The Oracle SID

The Oracle System Identifier (SID) identifies the Oracle instance on the machine It is usually set up as an operating system variable— the $ORACLE_SID environment variable in UNIX or the ORA_SID symbol in VMS—that is used to name of the Oracle background processes and to identify the SGA area in memory Whenever a user process wants to connect to a database, the SID set up in that operating system account determines to which instance and, therefore, to which database the user will connect The same user name can exist in different databases For example, the Oracle system username SYS exists in all Oracle databases With the SID, you can connect to the correct instance

Many instances might be running on the same machine, each doing the processing for a different database By looking at the processes running on the machine, you see many occurrences of the DBWR background process The name of the process itself usually has the SID somewhere in it

For client/server setups, the client machine identifies the network protocol and machine address to which the client machine wants to attach and the name of the SID of the connection Requests are then processed against the database for which the instance is processing

Creating a New Database

When you create a database, you create files on disk that Oracle has formatted and prepared The structure of the

database does not have to remain the same as initial structure You can add other files later

On some platforms, you can create a new database when the Oracle software is first installed To create a database manually after that, follow the steps in this section It is assumed that the software has been installed correctly on your machine The steps provided here are general steps that apply to most platforms Creating a database involves operating

system-specific steps, of course Refer to the Oracle7 Installation and User's Guide for their platform for specific

information on your platform

The crux of creating a database lies in running the CREATE DATABASE SQL statement You must perform other steps, however, before you can run it The syntax of the CREATE DATABASE SQL statement is

CREATE DATABASE mydb

LOGFILE file1, file2 SIZE nM

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For example,

CREATE DATABASE mydb

DATAFILE '/disk03/mydb/system1.dbf' SIZE 20M

LOGFILE '/disk04/mydb/log1.log',

'disk05/mydb/log2.log' SIZE 512K;

The datafile parameter will physically create the first database file on the disk specified and with the size specified If the file already exists the command will fail (unless the REUSE option is specified as well in which case the file will be over-written) The same is true with the LOGFILE parameter which creates the very first two redo log files

Dont use the REUSE option of the CREATE DATABASE command, for you could accidentally overwrite a file that is being used by another database Instead, physically delete the file You can use REUSE on some platforms when contiguous disk space that you want to reuse has already been allocated to a file

The default mode of the database is NOARCHIVELOG

To specify the maximum number of data files, redo logs, and log members that can exist on the database, use the

MAXDATAFILES, MAXLOGMEMBERS, and MAXLOGFILES parameters If you specify lower limits, fewer

resources are used in the SGA The MAXINSTANCES parameter controls the maximum number of instances that can

be connected to database

If you set these maximum limits lower than the predefined maximum as part of the CREATE DATABASE statement, you must recreate the control file manually to increase them Instead, you should specify the limits by using the INIT.ORA parameters, which set the limits for that startup of the instance That way, I you need to increase the limits, simply increase the INIT.ORA parameter and restart the instance

Leave the database mode set to NOARCHIVELOG—the default—in the CREATE DATABASE command Change the mode to ARCHIVELOG when all the application objects have been created and populated This improves performance while the application objects and data are initially loaded

The steps in creating new database are

1 Plan for the creation Make sure that there is adequate disk space for the database It is useful to do a sizing exercise to estimate the amount of storage required to hold the data for the application system Determine the names and locations of the database files, the control file, and the redo log files

Make sure that the memory on the machine is enough for the new database, including the memory for the SGA, the PGA, and the programs on the database server machine All the Oracle memory structures should fit into the machine's real memory

2 The operating system user account that you will use should have the INTERNAL privilege This privilege Please purchase PDF Split-Merge on www.verypdf.com to remove this watermark.

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enables your operating system account to run the CREATE DATABASE, STARTUP, and SHUTDOWN commands from the SQL*DBA tool A lower-level form of the INTERNAL privilege is the OSOPER and OSDBA roles INTERNAL, OSOPER, and OSDBA are assigned using operating system security

mechanisms—groups on a UNIX machine or process rights on a VMS machine Operating system administrators generally grant your account these privileges

3 Decide what the Oracle instance identifier is going to be, and set the appropriate operating system variable names The Oracle SID should not have the same as an existing instance on the same machine

4 Create the INIT.ORA file for your database The easiest way to do this is to copy an existing INIT.ORA file Rename this file to indicate the SID used for the instance—for example, INITMYDB.ORA Specify the name and location of the control file in the CONTROL_FILES parameter Specify the name of the

database—typically the same as the instance identifier— in the DB_NAME parameter The name of the database must match the name given in the CREATE DATABASE command It is recorded in all the database files, the control file, and the redo logs for the database If you want to change the DB_BLOCK_SIZE

parameter, you must do so now It cannot be modified later

5 Initiate the SQL*DBA tool, and make a connection to the Oracle RDBMS software by using the INTERNAL account Although the syntax of the CONNECT command looks similar to a normal connect, no password is specified:

SQLDBA> CONNECT INTERNAL

6 Start the Oracle background processes, and allocate memory for the SGA by starting up the Oracle instance For example,

SQLDBA> STARTUP NOMOUNT PFILE=INITMYDB.ORA

7 Run the CREATE DATABASE statement with the parameters specific to your requirements For example,

SQLDBA> CREATE DATABASE mydb DATAFILE '/disk03/mydb/system1.dbf' SIZE 20M

LOGFILE '/disk04/mydb/log1.log',

'disk05/mydb/log2.log' SIZE 512K;

Once the database has been created, it is immediately available for use No further steps are necessary At this stage, though, you have not created any objects on the database other than the ones automatically by the CATALOG.SQL file You can now start building the structure of your application database by defining tablespaces, usernames, tables, and so

on

You might need to run additional scripts to install the objects that enable the procedural database option or to store Oracle forms and other programs on the database

The First Objects Created

Many objects are present on the database immediately after you create it They are

● The Oracle users SYS and SYSTEM

● A tablespace called SYSTEM

● A rollback segment called SYSTEM

● The core data dictionary tables in the user account SYS

● The CONNECT, RESOURCE, and DBA roles, which that provide backward compatibility with granting privileges

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SYS has the default password CHANGE_ON_INSTALL, and SYSTEM has the default password MANAGER To test whether the database was created, try to make a connection using these user names and passwords The default

passwords should be changed The SYS account is the Oracle user that owns the core data dictionary tables There is usually little reason to use this account for day-to-day access to the database The SYSTEM account does not own any of the core data dictionary tables Instead, it uses a set of views created on them These views help the DBA and developers obtain information on the structure of the database and its objects

The first set of data files created as part of the CREATE DATABASE statement are allocated to the SYSTEM

tablespace Its initial contents are usually the data dictionary tables and other objects

Additional rollback segments should be created on the database

Along with the core data dictionary tables in the user account SYS, data dictionary views that make the information in the core tables easier to view and manage are created Public synonyms are created for most of the data dictionary views

to give Oracle users access to basic information on their user accounts

Startup and Shutdown

Before you can use an Oracle database, an instance must be running An instance is the combination of the Oracle

background processes and the SGA This section discusses how to initiate and shut down an instance

Startup Stages

For a database to be fully open and usable, the instance must be brought through three stages of startup:

1 Starting the instance

2 Mounting the database

3 Opening the database

The first stage involves initiating the Oracle background processes and allocating memory for the SGA During this stage, the INIT.ORA parameter file is used to determine the mode and instance initialization parameters, such as the sizes of the SGA structures in memory

The second stage is mounting the database It involves opening the control file—whose location is specified in the INIT.ORA parameter file used in stage 1—and determining the locations and names of the other database and redo log files

The third stage opens the actual database files and the redo logs Once this stage has been completed, you can access and use the database objects

In MOUNT or NOMOUNT state, the database can be used only by the DBA

In some cases, such as when recovery is to be initiated, the database might not have gone through all three stages For example, it might be at stage 2, which means that that only the control file can be accessed The actual database files are closed, so no operations on database objects are possible

The tool used to perform the startup and shutdown is the Oracle SQL*DBA utility, which comes with the database Please purchase PDF Split-Merge on www.verypdf.com to remove this watermark.

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software This tool has a basic menu and Òfill in the blankÓ screens

Before we can issue a startup or shutdown from the SQL*DBA tool, you must be connected as the INTERNAL user by means of a dedicated server connection In other words, the multi-threaded server configuration cannot be used This is a check whether you have operating system privileges and can perform these operations Operating system-specific privileges, such as UNIX groups or VAX VMS process rights, determine who has access to perform these operations

Once you are connected as the INTERNAL user, you can use the STARTUP command to initiate the instance startup in whatever mode you want During the first stage of startup, the instance parameter file must be provided In its simplest form, the startup command brings the instance through all three stages and makes the database available for all Oracle users to access:

SQLDBA> STARTUP

Note that he parameter file that the instance will use has not been specified On most platforms, you can set an operating system environment variable The default location for the parameter file on a UNIX platform is the /dbs directory under the home directory of the Oracle software

The name of the database is assumed to have been specified in the INIT.ORA parameter file with the DB_NAME parameter The name of the database specified is checked against the name of the database stored in the control file If a mismatch occurs, the instance fails to start up and an error message is generated

If you do not use this syntax, you must name the parameter file explicitly in the STARTUP command In the following command, the DB_NAME parameter has not been specified in the INIT.ORA file Therefore, you must specify it

explicitly as part of the STARTUP command

SQLDBA> STARTUP PFILE ='/disk04/initmydb.ora' db_mydbname

You can also use this syntax when you want to start up the instance with a set of parameters different from the default values For example, you might want to use parameters that have been tuned to optimize batch jobs

If you use the parallel server option, you can specify additional parameters as part of the STARTUP command The PARALLEL and EXCLUSIVE parameters control whether other instances can access the database once the instance has started up If you use the EXCLUSIVE parameter, any attempt to start up the instance on another processor fails

In many cases, you might not want to take the instance through all three stages For example, you might need to perform maintenance and recovery operations If this is the case, specify additional parameters, depending what stage you want

If you use NOMOUNT parameter, only the Oracle background processes start and the SGA area in memory is allocated You typically use NOMOUNT only when the database is created For example,

SQLDBA> STARTUP PFILE ='/disk04/initmydb.ora' NOMOUNT

The MOUNT option takes the instance up to the point when the control file is opened You use MOUNT, for example, when you want to recover the database and the database files or redo logs are not present You need to have the control file open, which is the case if the database is mounted, because it contains information that helps ensure that the files that make up the database remain in a synchronized state For example,

SQLDBA> STARTUP PFILE ='/disk04/initmydb.ora' MOUNT mydbname

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The next word after MOUNT or OPEN in the STARTUP command is assumed to be the name of the database

If the name of the database has already been specified in the INIT.ORA file, move the MOUNT or OPEN keyword to the end of the command

Another option is to bring the database through all three stages but to limit access to the tables to the DBA This is useful for performing a full export of the database, because the data will not change during the export For example,

SQLDBA> STARTUP PFILE ='/disk04/initmydb.ora' RESTRICT OPEN

Only Oracle accounts that have been given the RESTRICTED SESSION system privilege can connect to the database after the instance is brought up with the RESTRICT keyword

On some operating systems, a special facility is provided to databases to be started automatically when the machine is booted up Refer to the user's guide for your platform to see how to implement this facility if it is available on your platform

Shutdown Stages

A database is brought down in three stages:

1 Closing the database files and the redo log files

2 Dismounting the database

3 Shutting down the Oracle background processes and releasing the memory occupied for the SGA

In the first stage, the database files and the redo log files are closed Before this happens, information in the SGA is flushed down to the database files for system and user data Entries from the redo buffer cache in the SGA are also flushed down to the active redo log file, and a marker is made in the redo log to indicate that a shutdown has occurred

In the second stage, the database is dismounted This means that the control file is updated with synchronization

information and closed

In the third stage, the Oracle background processes are shut down, and the memory occupied for the SGA is released

The SQL*DBA tool is used to perform the shutdown, and the user must be connected to the database as INTERNAL For example,

The SHUTDOWN command takes the instance through all three shutdown stages:

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If users are connected to the database, the SHUTDOWN command without any parameters waits indefinitely for them to disconnect from the database You can disconnect users manually by using the ALTER SYSTEM KILL

SESSION command or by means of the SQL*DBA menu options

You can shut down the instance so that connected users are immediately disconnected and work in their current

transactions is rolled back Use the IMMEDIATE keyword after the SHUTDOWN command:

SQLDBA> SHUTDOWN IMMEDIATE

You should send a message notifying all the users currently connected to disconnect from the database There is no Oracle facility for doing this, so you must use an operating system utility This is a problem especially for client/server setups, because the users might be running the tools on another machine

In extreme cases, you can shut down the instance without waiting for information to be flushed from the SGA to the database and redo log files Use the ABORT option of the SHUTDOWN command:

SQLDBA> SHUTDOWN ABORT

Like the IMMEDIATE option, ABORT disconnects all the users currently connected, but the rollback operation is not be performed when the instance is shut down Instead, if a rollback is performed, it happens the next time the instance is started up This option is quicker than the IMMEDIATE option, especially when a large update transaction has to be rolled back before the instance can be shut down Essentially, the rollback is delayed until you next start up the instance

A more cruder way of bringing down the database on some platforms is to kill the Oracle background processes that are currently running If the background processes are no longer running, the instance is not up This method is not

recommended, though

Regardless of how you bring the instance down, the integrity of the database is not in any danger The values of any changes are recorded in the redo logs; on COMMIT, they are forced to the redo log files on disk Changes to the

database blocks in the database buffer cache in the SGA that have not been written to the database files before

SHUTDOWN IMMEDIATE, SHUTDOWN ABORT, or even an instance crash, are reapplied automatically the next time the instance is brought up This is totally invisible to the user and the DBA The only noticeable effect after

SHUTDOWN IMMEDIATE or SHUTDOWN ABORT is a increase in the time taken during the opening stage of bringing up the instance

Suppose that you started the instance in NOMOUNT or MOUNT state and need to take it from one stage of startup to another The easy way to do this is to shut down the instance entirely and then restart it in the mode you want Likewise, you could use the ALTER DATABASE command, which takes the database from one stage of startup to another Refer

to the Oracle SQL Language Reference Guide for more information on this command

The Data Dictionary

The Oracle data dictionary is a set of tables that the Oracle software uses to record information about the structure of the database These core system tables are owned by the Oracle user present on all Oracle databases—the SYS user SYS is rarely used, even by DBAs, for maintenance or inquiry work Instead, another Oracle user with a high-level system privileges is used Typically, only one other DBA account is created for the user of the DBA

The DBA does not usually use the SYSTEM user, which is also automatically defined when the database is created This

is because product-specific tables are installed in SYSTEM, and accidental modification or deletion of these tables can Please purchase PDF Split-Merge on www.verypdf.com to remove this watermark.

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