A Guide to Oracle9i1 Introduction to Oracle9i Database Administration Chapter 11.

A Guide to Oracle9i 1

Introduction to Oracle9i Database Administration

Chapter 11


Lesson A Objectives

• Become familiar with database administration tasks• Understand the process for installing an Oracle9i

database, configuring client applications, and removing Oracle9i applications

• Learn how to use Oracle9i Enterprise Manager to perform database administration tasks

• Understand Oracle9i data storage structures• Become familiar with Oracle9i database files


Overview of Database Administration

DBA tasks include:• Install and upgrade the DBMS software on the server• Optimize database performance by configuring how

the database uses storage space in the server’s main memory and file system

• Create and maintain user accounts to control database access

• Monitor data storage space and allocate additional storage space as needed

• Start and shut down the database to perform database maintenance tasks


Overview of Database Administration

• Perform backup and recovery operations• Install and upgrade developer client utilities (such as

Forms Builder and SQL*Plus) on developer client workstations

• Deploy finished database applications to users• Assist developers in designing and creating database

tables• Assist developers in designing and creating form and

report components and integrated database applications

• Assist in testing and debugging new applications• Assist in training developers and users


Installing an Oracle9i Database

The three Oracle9i DBMS levels are:

• Enterprise Edition - the most powerful DBMS, and is appropriate for installations that require a large number of transactions performed by multiple simultaneous users

• Standard Edition - sufficient for high volume multiple-user installations

• Personal Edition - provides a single-user DBMS for developing database applications.



• Universal Installer utility– Allows you to view the Oracle Corporation

products that are installed on a workstation– Guides you through the process of installing new

products– Allows you to uninstall Oracle9i applications



• Universal Installer displays the following pages for the Oracle9i database installation:

– File Locations page: specifies the location of the application source files and the location and name of the Oracle Home to which you wish to install the application

– Available Products page: displays a menu showing the different products available for installation

– Installation Types page: displays installation options for the selected product



– Database Configuration page: specifies the properties of the preconfigured database that Universal Installer creates

– Database Identification page: specifies the database name and instance name values that uniquely identify the database

– Database File Location page: specifies the drive letter and folder path in which the database stores the files that contain the actual database data values


Installing An Oracle9i Database

– Database Character Set page: specifies the character set or sets that the database uses to store character data

– Configuration Tools page: configures properties of the predefined database and configures the database network properties

– End of Installation page: signals the end of the installation process, and provides messages and other details about the installation process


Configuring Client Applications to Connect to an Oracle9i Database

• To connect to an Oracle9i database, you type a connect string in the Host String field on the Log On dialog box in SQL*Plus, or in the Database field in the Connect dialog box in Forms Builder

• The connect string provides Oracle Net the information it needs to create a connection between the client application and a specific database instance



• To configure connect strings for client applications that connect to databases that are not on the same workstation as the database server, you use one of the following approaches:– Local naming– Oracle Internet Directory



• Local Naming - The local naming approach stores connect string and database connection information in a file named tnsnames.ora on the client workstation

• Oracle Net uses a connect descriptor to route a client data request to a specific Oracle9i DBMS. It specifies:– Network communication protocol

– IP address of the database server

– Database instance name



• Oracle Internet Directory stores connect descriptor and service name information on a directory server called an Oracle Internet Directory (OID) server

• A directory server specifies the location of servers on a network

• An OID server uses the Lightweight Directory Access Protocol (LDAP) which is a standard protocol for configuring a directory server– LDAP specifies that the directory server contains entries for

each server process in a specific format



• To use an Oracle Internet Directory server– a client database application requests to connect

to an Oracle9i database by contacting the OID server and specifying the LDAP server entry for the desired database, as shown in the next slide


Removing an Oracle9i Database• You can use Universal Installer to remove Oracle9i

applications from a server or workstation• Universal Installer does not remove all elements from the

registry• To completely remove an Oracle9i database or client

application from a workstation, you must perform the following operations:

– Manually edit the system registry to remove all Oracle9i-related entries

– Restart the workstation– Manually delete all Oracle9i-related files and folders


Using OEM to Perform DBA Tasks

• OEM = Oracle Enterprise Manager – a utility that allows DBAs to perform database administration support tasks

• Universal Installer installs OEM on the server or workstation when you install any Oracle9i database

• OEM has a three tier architecture as shown in the next slide



Oracle Enterprise Manager Architecture



• Console – where the DBA performs administration tasks

• Oracle Management Server – an Oracle9i database server that supports database administration tasks in an organization. The OMS interacts with the repository

• Repository – contains information for remotely administering different databases

• The OMS then interacts with different database servers in Tier 3



• Through OEM you access different database objects to perform various database administration tasks

• Database objects include: instance, schema, security, storage, distributed, warehouse, workspace, XML database



• Instance - provides information about the database instance, allows the DBA to edit instance information, and allows the DBA to start up and shut down the instance

• Schema - allows the DBA to examine and manipulate database objects (such as tables, sequences, indexes, and views) in all user schemas

• Security - allows the DBA to create and manage user accounts

• Storage - provides information about existing database storage structures and allows the DBA to create and configure storage structures



• Distributed - allows the DBA to support applications and databases that are distributed across multiple database servers

• Warehouse - provides applications that allow DBAs and database developers to analyze database contents and look for long-term trends

• Workspace - allows DBAs and other users to view and maintain different versions of the same data

• XML Database - allows DBAs and database developers to create an XML database based on Oracle9i database tables


Managing Oracle9i Data Storage

• Data structure provides a framework to organize data that a computer stores

• Tables, lists, and arrays are examples of data structures

• Oracle9i data structures have a hierarchical relationship



• Database Instance – stores data in one or more tablespaces

• Tablespace - stores related database objects• Segments - stores an individual database object,

such as a table or an index• Extent - a contiguous unit of storage space within a

segment• Data Block - smallest storage unit that the database

can address. Extents consist of data blocks



• Each Data Block consists of: header, free space and row data

• Header - contains information about the data block contents, and is made up of three separate subsections: the block header, the table directory, and the row directory

• Free space - is empty space that the block retains in case users update the data within the data block, and the updated data occupies more storage space than the original data

• Row Data – stores actual data values



Data Block Components


The Oracle9i Database File Architecture

• An Oracle9i database is made up of several different files that reside in the file system of the database server workstation. These files include:

• Parameter files - initialize the database specifications and point to the locations of the database control file

• Control files - contain information about the database tablespaces, datafiles, redo log files, and the current state of the database



• Datafiles – contain the actual data values• Redo log files - contain rollback information for

uncommitted transactions • An Oracle9i database stores rollback information in

redo log files in a data structure called a rollback segment

• A rollback segment is made up of data blocks configured in a circular fashion

• As users perform action queries, the DBMS adds new rollback information to the rollback segment data blocks



Rollback Segment


Lesson B Objectives

• Create and manage user accounts• Understand an Oracle9i database instance’s memory

areas and background processes• Learn how to start and shut down the database• Understand Oracle9i database backup and recovery


Creating and Managing User Accounts

• When you create a new user account you must specify the following:

– Username, Password, default tablespace and temporary tablespace

– System privileges the user has in the database– User’s tablespace quota on the database server



• System Privilege - allows a user to perform a specific task with the Oracle9i database, such as connecting to the database or creating a new table

• Object Privilege - allows a user to perform a specific action on a database object, such as selecting data from a table or retrieving a value from a sequence



• Tablespace Quota - A user’s tablespace quota specifies– Amount of disk space that the user’s database objects can

occupy in his or her default tablespace

• A role is a database object that represents a collection of system privileges that you can assign to multiple users


Components of an Oracle9i Database Instance

• In an Oracle9i client/server database, a client process that runs on the client workstation connects to a database instance that runs on the database server

• The link between the client process and the database instance is called a connection, and it creates a user session

• A database instance consists of a set of processes and associated memory structures that manipulate data in a database’s tablespaces



• An Oracle9i database instance creates two memory areas in the database server’s main memory: – System Global Area– Program Global Area

• The System Global Area (SGA) is a memory area that all database connections use. The purpose of the SGA is to share information among all database processes. The SGA is made up of five primary memory areas: shared pool, database buffer cache, large pool, redo log buffer, Java Pool



Primary Memory Areas Within the System Global Area



• The Program Global Area (PGA) is a memory area that stores information for a specific user connection. The PGA contains two separate memory areas : session information and stack space

• The session information area contains information about the user session, such as the username, time the session started, date of the last activity, and global variable values

• The stack space contains the values of the variables that the user declares in PL/SQL programs and other programs



Memory Areas Within the Program Global Area



• An Oracle9i database instance contains a set of background processes to service user requests

• The Oracle9i background processes include: DBWn, LGWR, SMON, PMON, and CKPT

• DBWn - writes changed data from the database buffer cache to the datafiles

• LGWR - writes redo information from the redo log buffer to the redo log files



• SMON - has three primary functions:– Recover lost data after a system hardware or software failure– Deallocate temporary memory areas that the database uses for

sort operations– Manage server disk space by periodically coalescing free space to

make larger continuous extents for new data

• PMON - monitors and manages individual user sessions

• CKPT - responsible for initiating checkpoints. A checkpoint signals the DBWn and LGWR processes to write the buffer contents to the datafiles and redo log files


Starting and Shutting Down the Database

• Database administrators must shut down a database periodically to perform maintenance tasks such as:– Backing up the database– Adding new datafiles– Modifying the properties of the parameter file– Recovering from a database crash

• After the DBA performs the maintenance activity, he or she restarts the database to make it available for new user connections



• When a DBA shuts down an Oracle9i database instance, the DBA has four different options for how the shutdown process handles existing user connections:– Normal– Transactional– Immediate– Abort



• Normal - instance does not accept any new connections, but allows current users to finish their transactions and log off normally

• Transactional - instance does not accept any new connections, and allows users to finish their current transaction

• Immediate - instance does not accept any new user connections, and immediately terminates current user connections

• Abort - immediately disconnects all users, stops the instance’s processes, and reallocates all server memory



• When a DBA starts an Oracle9i database instance, he or she can start it in one of three modes: – Unrestricted: allows all users to create

connections– Restricted: creates connections only for users who

have the RESTRICTED SESSION system privilege

– Read-only: allows users to read database contents, but does not allow users to perform action queries that modify database contents



• When a DBA shuts down a database instance using the Normal, Transactional, or Immediate shutdown option, the shutdown process performs the following tasks:– Writes the contents of the data buffer cache to the datafiles– Writes the contents of the redo log buffer to the redo log files– Closes all files– Stop all background processes– Deallocates the SGA in the server’s main memory

• NOTE: When a DBA restarts a database instance, the startup process performs these tasks in the reverse order


Database Backup and Recovery

• Important database administration support tasks include– Backup: creating a copy of the database files– Recovery: restoring the database to a working

state after a hardware or software malfunction

• Backup operations on an Oracle9i database can be classified as:– Offline (cold) backups– Online (hot) backups


Database Backup and Recovery

• Offline Backup – (cold backup) requires shutting down the database, then copying all of the database files to an alternate location

• Online Backup – (hot backup) involves backing up critical database files while the instance is running, as well as creating an ongoing archive of database changes so the DBA can restore the database to its state at any point in time


Summary• Database administration involves installing, configuring,

maintaining, and troubleshooting a database

• Oracle9i database exists at three levels: Enterprise Edition, Standard Edition, and Personal Edition

• Universal Installer pages guide you through the installation process

• You can use local naming to configure client applications to connect to an Oracle9i database

• OEM allows DBAs to perform database administration support tasks


Summary

• A database instance stores data in one or more tablespaces

• Parameter file specifies configuration information about an Oracle9i database instance

• Control files store information about the database structure and state

• Redo log files record information to undo action query changes through user rollback operations

• An Oracle9i database stores the rollback information in a rollback segment


Summary

• When creating a new user account, you must specify general information about the user account, system privileges, and the user’s tablespace quota

• System privileges allow users to perform specific tasks with the Oracle9i database

• A role represents a collection of system privileges that you can assign to multiple users


Summary

• An Oracle9i database instance creates the System Global Area (SGA) and the Program Global Area (PGA)

• DBA can start an Oracle9i database instance in unrestricted, restricted or read-only mode

• Backup involves creating a copy of the database files, and recovery involves restoring the database to a working state after a hardware or software malfunction

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A Guide to Oracle9i1 Introduction to Oracle9i Database Administration Chapter 11.

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