oracle 8 database administration volume 1 instruction guide phần 3 ppt

Objectives • Setting up operating system and password file authentication • Creating the parameter file • Starting up an instance and opening the... Every time an instance is started, Or

3

Managing

an Oracle Instance

Objectives

3-2 Copyright  Oracle Corporation, 1998 All rights reserved.

Objectives

• Setting up operating system and

password file authentication

• Creating the parameter file

• Starting up an instance and opening the

An Oracle database is not available to users until the database administrator

has started the instance and opened the database

During a database startup, the following events occur that take the Oracle

database through various stages:

1 Start an instance

2 Mount the database

3 Open the database

Every time an instance is started, Oracle uses a parameter file, which

contains initialization parameters, to allocate the SGA and to start the

background processes

If an instance is started or a database is open, you can follow these steps to

shut down the database:

1 Close the database

2 Dismount the database

3 Shut down the instance

When a database is closed, users cannot access it Starting up and shutting

down are covered in detail later in this lesson

3-3 Copyright  Oracle Corporation, 1998 All rights reserved.

User

process

Server process

PGA

Password file

ALERT file Parameter file

Overview

Control files

Data files Redo log files

Instance SGA Shared pool

Validating Privileged Users

Validating Privileged Users

3-4 Copyright  Oracle Corporation, 1998 All rights reserved.

Database Administrator Users

• Automatically created

• Granted the DBA role

The two database administrator users

SYS and SYSTEM are:

3-5 Copyright  Oracle Corporation, 1998 All rights reserved.

User SYS and SYSTEM

The Database Administrator Users

Extra privileges are necessary to execute administrative duties in Oracle

such as creating users These operations must be performed by database

administrators

Two database user accounts, SYS and SYSTEM, are automatically created

with the database and granted the DBA role—that is, a predefined role that is

automatically created with every database The DBA role has all database

system privileges

Note

This subject is covered in more detail in the lesson “Managing Privileges.”

SYS

When a database is created, the user SYS, identified initially by the

password CHANGE_ON_INSTALL, is automatically created and granted

the DBA role

All of the base tables and views for the data dictionary are stored in the

schema SYS

SYSTEM

When a database is created, the user SYSTEM, identified initially by the

password MANAGER, is also automatically created and granted the DBA

role privileges for the database

In the schema SYSTEM, additional tables and views are created that contain

administrative information used by Oracle tools

Note

You will probably want to create at least one additional administrator

username to use when performing daily administrative tasks

Instructor Note

Briefly define the term schema as a synonym of user and explain that this

subject will be covered in more detail in the security lessons

Validating Privileged Users

Connecting with Administrator Privileges

In some cases the database administrator needs a special authentication

method, because the database may not be open, especially for operations

like shutdown and startup

Depending on whether you want to administer your database locally on the

same machine on which the database resides or to administer many different

database servers from a single remote client, you can choose either operating

system authentication or password files to authenticate database

Use OS authentication

Use a password fileAuthentication Methods

Setting up the user to be authenticated by an operating system authentication

on a UNIX system is different from setting up a user for authentication on an

NT system

UNIX

1 The user must be a member of the UNIX group, usually called dba, that

is created before the Oracle Server is installed The installer assigns

Oracle database administrator and operator privileges to this UNIX

group

2 View the files /etc/group and /etc/passwd to determine the members of

the UNIX group

The following lines are an excerpt from the /etc/passwd file:

• Set up the user to be authenticated by

the operating system.

Validating Privileged Users

3 Make sure that the REMOTE_LOGIN_PASSWORDFILE parameter is

NONE, which is the default value for this parameter

4 Connect to the database with the privilege SYSDBA or SYSOPER—

these are special database administrator privileges This implies

connecting in the schema owned by SYS:

CONNECT / AS {SYSDBA |SYSOPER }

Note

Using the privileges SYSDBA and SYSOPER is covered in the lesson

“Managing Privileges.”

NT

1 Create a new local Windows NT users’ group called ORA_<SID>_DBA

and ORA_<SID>_OPER that is specific to an instance, or ORA_DBA

and ORA_OPER that is not specific to an instance

2 Add a Windows NT operating system user to that group Once you

access this domain, you are automatically validated as an authorized

DBA

3 Set the REMOTE_LOGIN_PASSWORDFILE to NONE

4 Connect to the database with the privilege SYSDBA or SYSOPER:

CONNECT / AS { SYSDBA|SYSOPER }

Note

• To connect to a Windows NT server from a local, remote Windows NT

or Windows 95 client, NET8 must be installed on both the client and the

server

• The use of the command CONNECT INTERNAL used with earlier

versions of Oracle has been replaced by the new syntax:

CONNECT INTERNAL/pw AS SYSDBA

CONNECT INTERNAL continues to be supported for backward

compatibility only

• Oracle no longer supports setting DBA_AUTHORIZATION parameter

in the registry to BYPASS to enable connections without the use of a

password

Using Password File Authentication

Oracle provides a password utility that allows connection to the Oracle

Server using a standard username and password, but that connects the user

to the SYS schema instead of as the username provided Access to the

database using the password file is provided by special GRANT commands

issued by privileged users (see the lesson “Managing Privileges.”)

Using a Password File on a UNIX and an NT Server

1 Create the password file using the password utility ORAPWD on UNIX

or ORAPWD80 on NT

orapwd file=<fname> password=<password> entries=<entries>

where:

database administratorsThe following command creates a password file with the password

“admin” for the user SYS and INTERNAL and accepts up to five users

with different passwords:

$orapwd file=$ORACLE_HOME/dbs/orapwU15 password=admin entries=5

3-8 Copyright  Oracle Corporation, 1998 All rights reserved.

Using Password File Authentication

• Create the password file using the

Validating Privileged Users

2 Set the REMOTE_LOGIN_PASSWORDFILE parameter to

EXCLUSIVE or SHARED

where:

EXCLUSIVE indicates that only one instance can use the

password file and that the password filecontains other names than SYS andSYSTEM

SHARED indicates that more than one instance can

use the password file (The only usersrecognized by the password file are SYS

• The password for INTERNAL is “oracle,” if Oracle is installed through

the Oracle8 Enterprise Edition option You can set the password during

installation by using the Custom installation option

Changing the Internal Password

On UNIX and NT, delete the existing password file and create a new

password file using the ORAPWD utility

In addition, on NT you can use the ORADIM80 utility to recreate the

password file

C:\>ORADIM80 -NEW -SID sid [-INTPWD internal_pwd][SRVC svrcname] [MAXUSERS n][STARTMODE auto, manual][-PFILE filename]

where:

sid specifies the instance name

internal_pwd is the password for the internal account

n is the maximum number of entries of the

password file

auto or manual indicates whether the service start mode is

manual or automatic

used to configure the instance

3-9 Copyright  Oracle Corporation, 1998 All rights reserved.

Changing the Internal Password

• Use the password utility on NT and UNIX

to delete and create the password file.

or

• Use the ORADIM80 utility on NT to delete

and create a new password file.

Validating Privileged Users

To change the INTERNAL password, follow the steps:

1 Delete the SID for the password you want to change:

C:\> ORADIM80 -DELETE -SID sid

where sid is the SID to delete

2 Create the same SID again and specify a new INTERNAL password:

C:\> ORADIM80 -NEW -SID sid -INTPWD internal_pwd - MAXUSERS N

where SID is the same SID to recreate

Instructor Note

For more information about the ORADIM80 utility see the manual Oracle8

Enterprise Edition Getting Started Release 8.0.4 for Windows NT.

Creating a Parameter File

The parameter file, commonly referred to as the init<SID>.ora file, is a text

file that can be maintained using a standard operating system editor

By default, it is located in the $ORACLE_HOME/dbs directory on a UNIX

machine and in the %ORACLE_HOME%\database directory on NT

The parameter file is read only during instance startup If the file is modified,

shut down and restart the instance to make the new parameter values

effective

Note

Oracle Enterprise Manager must be able to read the parameter file to start an

instance of a database Therefore starting a remote instance or database

requires the parameter file to be stored on the computer that is executing

Oracle Enterprise Manager

However, Oracle Enterprise Manager can also store the parameter

configurations This enables you to create multiple database startup

configurations without the need to track initialization parameter files Stored

configurations exist in the registry and not as external files

3-10 Copyright  Oracle Corporation, 1998 All rights reserved.

The Initialization Parameter File

SVRMGR> CONNECT / AS SYSDBA

SVRMGR> STARTUP PFILE=/DISK1/initU15.ora

initU15.ora

Instance SGA Shared pool

Library cache Redo log

buffer

PMON DBWR SMON CKPT LGWR ARCH

Database buffer cache

Data dictionary cache

Creating a Parameter File

To create or modify a stored configuration:

1 Use Instance Manager

2 Select Initialization Parameters

3 Choose Save on one of the property sheets

4 Enter a configuration name in the Configuration property sheet

Instructor Note

The parameter file can also reside on a device mounted by the computer, for

example, in a shared directory in an NFS mounted file system

Uses of Parameters

The parameters in the init <SID>.ora file can have a significant effect on

database performance, and some need to be modified in the following ways

for production systems:

• Size the System Global Area (SGA) components to optimize

performance

• Set database and instance defaults

• Set database limits

• Define (on database creation only) various physical attributes of the

database, such as the database block size

• Specify control files, archived log files, and trace file locations

Rules for Specifying Parameters

• Specify the values in the following format: keyword=value

• All parameters are optional

• The server has a default value for each parameter

• Parameters can be specified in any order

• Comment lines begin with the # symbol

• Enclose parameters in double quotation marks to include character

literals

• Additional files can be included with the keyword IFILE

• If case is significant for the operating system, then it is also significant in

filenames

• Multiple values are enclosed in parentheses and separated by commas

Note

Develop a standard for listing parameters; either list them alphabetically or

group them by functionality

3-11 Copyright  Oracle Corporation, 1998 All rights reserved.

Parameter File Example

# Initialization Parameter File: initU15.ora

Creating a Parameter File

Parameters That Should Be Specified

Instructor Note

These are only a few examples; the following lessons cover more

initialization parameters For a complete list, see the manual Oracle8

Reference, Release 8.0.

BACKGROUND_DUMP_DEST Location where background process trace files

are written

COMPATIBLE Version of the server with which this instance

should be compatible The default is 8.0.0CONTROL_FILES Names of the control files

DB_BLOCK_BUFFERS Number of blocks cached in the SGA The default

and the minimum is 50 buffers

DB_NAME Database identifier of eight characters or fewer

This is the only parameter that is required whencreating a new database

SHARED_POOL_SIZE Size in bytes of the shared pool

The default is 3500000

USER_DUMP_DEST Location where user trace files are created

Commonly Modified Parameters

IFILE Name of another parameter file to be

embedded within the current parameterfile Up to three levels of nesting ispossible

LOG_BUFFER Number of bytes allocated to the redo log

buffer in the SGA

MAX_DUMP_FILE_SIZE Maximum size of the trace files, specified

as number of operating system blocks.PROCESSES Maximum number of operating system

processes that can connect simultaneously

to this instance

SQL_TRACE Enable or disable the SQL trace facility

for every user session

TIMED_STATISTICS Enable or disable timing in trace files and

in monitor screens

Stages in Startup and Shutdown

Stages in Startup and Shutdown

Starting Up in Stages

When starting the database, you choose the state in which it starts

The following scenarios describe different stages of starting up an instance

Starting the Instance

Usually you would start an instance without mounting a database, only

during database creation or the recreation of control files

Starting an instance includes the following tasks:

• Reading the parameter file init<SID>.ora

• Allocating the SGA

• Starting the background processes

• Opening trace and ALERT files

The database must be named either with the DB_NAME parameter in the

init<SID>.ora file or in the STARTUP command.

3-12 Copyright  Oracle Corporation, 1998 All rights reserved.

Control file opened for this instance.

Instance started.

SH

U TD

O WN STARTUP

Startup and Shutdown in Stages

Mounting the Database

To perform specific maintenance operations, you start an instance and mount

a database, but do not open the database

For example, the database must be mounted but not open during the

following tasks:

• Renaming data files

• Enabling and disabling redo log archiving options

• Performing full database recovery

Mounting a database includes the following tasks:

• Associating a database with a previously started instance

• Locating and opening the control files specified in the parameter file

• Reading the control files to obtain the names and status of the data files

and redo log files (However, no checks are performed to verify the

existence of the data files and online redo log files at this time.)

Opening the Database

Normal database operation means that an instance is started and the database

is mounted and open; this allows any valid user to connect to the database

and perform typical data access operations

Opening the database includes the following tasks:

• Opening the online data files

• Opening the online redo log files

If any of the s or online redo log files are not present when you attempt to

open the database, Oracle returns an error

During this final stage, Oracle verifies that all the s and online redo log files

can be opened, and checks the consistency of the database If necessary, the

background process System Monitor (SMON) initiates instance recovery