Tutorial HK:Configuring Oracle on Linux For

Peak Performance

Roger Schrag

Database Specialists, Inc.

www.dbspecialists.com

LinuxWorld Conference & Expo

August 10, 1999

Today’s Presentation

• Introduction to Oracle technology

• Installing Oracle

• Managing your database

• Optimizing your database

• Where to get more information

About The Author

• 10+ years experience with Oracle technology

• Lots of Oracle DBA experience on Unix platforms

• Mostly e-business and ERP systems

• Presenter at Oracle user groups and conferences

• Author of various white papers

• Linux believer

Today’s Goals• Get a basic understanding of “How Oracle

Works”

• Learn the proper way to install Oracle

• Gain access to accurate information

Oracle Quick Start

• Learn basic Oracle concepts

• Install Oracle software

• Create a default database

• Make the default database usable

• Create application schema

• Develop application

• Big picture issues (backups, capacity planning…)

An Introduction to Oracle Technology

• Platform independence

• Database terminology

• Important files

• Oracle process architecture

• Environment variables

• Optimal flexible architecture

• Interacting with a database

Platform Independence

• Abstraction of platform-specific issues

• Generic and platform-specific documentation

• Oracle skills transfer well from one platform

to another

Database Terminology

• Key fundamentals

• Learn them correctly

• Many “Oracle-isms”

Terminology

DBA• Stands for “database administrator”• Involved in logical design of a

database• Performs the physical design and

implementation• Assists developers with difficult

database issues• Responsible for ensuring good

performance, proper security, as well as backup and recovery strategies

Terminology

Database

• A collection of operating system files that

make up one physical data store or node

• Many different types of data, each with its

own attributes, can be stored in one database

Terminology

Database Name

• Every Oracle database has a name

• Eight characters or less

• Default global domain name is “.WORLD”

• Best to give each database a unique name and use one common domain

Terminology

Instance

• A set of operating system processes and shared memory structures which allow an application to access data in a database

Terminology

Instance Name

• Also known as SID (System Identifier)

• Applications identify which instance they

wish to access by name

• The convention is to give an instance the

same name as the database it accesses

Terminology

• Stands for System Global Area

• A collection of shared memory structures

created by an Oracle instance

• Each process of the instance attaches itself to

the SGA upon startup

SGA

Terminology

Starting the Database

• Opening a database so that applications may access it

• Done by starting up an instance and mounting it to the database

Terminology

Net8 or SQL*NET

• Networking infrastructure that allows applications to access databases on remote servers

• Was called SQL*Net before Oracle8• Renamed to Net8

Terminology

Client/Server

• Oracle internally uses a client/server architecture

• The application accessing Oracle is seen as the client, the Oracle server process is a server

Terminology

Username

• Each user in an Oracle database has a unique name up to 30 characters in length

• Separate usernames in the database do not need to map to separate real-life users

Terminology

Schema

• A separate namespace for database objects such as tables, indexes and stored procedures

• Every database object resides in one schema

• Each database user has one schema with the same name as their username

• Username = schema

Terminology

Data Dictionary

• Repository of information indicating all of the users defined in the database and all of the objects they own

• A set of database tables with names like user$ and tab$

Terminology

SYS and SYSTEM

• SYS user owns all of the internal structures that make up the data dictionary for the database

• SYS user has all privileges on the database

• SYSTEM user has DBA privileges also

Terminology

Control Files, Data Files, Redo Logs and Parameter Files

• The physical files that make up an Oracle database

Terminology

Tablespace

• A named collection of one or more physical files used for storing database objects

• Mask certain implementation details from application developers

Terminology

Extent

• One contiguous chunk of physical storage

within a tablespace

• Can range in size from 2 Kb to 2 Gb, but must

be contiguous

Terminology

Segment

• A collection of extents that belong to one object

• Physical storage used to hold the data for an object

• Most hold the contents of a table or index, but there are other types of segments as well

Terminology

Rollback Segment

• Stores “undo” information for a transaction that is still in progress

• Allows Oracle to back out the transaction if the application requests a rollback

• Enables one session to update data while another is querying the same data

Terminology

Temporary Segment

• Holds a partial result set when too much data

is involved to complete the operation in

memory

• Commonly used when sorting data for

ordering, grouping, or building an index

Terminology

Identifier

• Most are limited to 30 bytes in length and are

case-insensitive

• Unless quoted, identifiers must start with a

letter and may include letters, digits and

certain special characters like _, $, and #

Terminology

The Files That Control an Oracle Instance

• Parameter file

• Password file

The Files That Make Up a Database

• Control files

• Data files

• Online redo logs

• Archived redo logs

The Oracle Process Architecture

• Database

• Instance

• Net8

• Applications

The Oracle Instance

• Shared global area (SGA)

• Daemon processes

• Server processes

Oracle Daemons

Process Monitor PMONSystem Monitor SMONLog Writer LGWRDatabase Writer DBWnCheckpoint CKPTArchiver ARCHRecoverer RECOJob Queue SNPnLock LCKn

Oracle Process Architecture

Making an Oracle Database Available

1. Start an instance

2. Mount the database

3. Open the database

Accessing a Local Database

1. Application forks an Oracle server process

2. Environment variable indicates which local database to access

3. setuid bit allows server process to attach to SGA, read data files

4. Application communicates with server process via IPC

Accessing a Remote Database

1. Net8 client resolves alias to hostname, port, and instance name (in the case of TCP/IP protocol; other protocols supported)

2. Net8 client sends a request to the Net8 listener on the database server

3. Net8 listener on database server forks an Oracle server process

4. Application communicates with server process using any supported protocol

Environment Variables

• ORACLE_HOME

• LD_LIBRARY_PATH

• PATH

• ORACLE_SID

• TWO_TASK

• NLS_LANG

• ORA_NLS33

• ORACLE_BASE

• DBA

$ORACLE_HOME

• Location of Oracle software installation

• For example: /u01/app/oracle/product/8.0.5

• Always required

$LD_LIBRARY_PATH

• Location of Oracle shared libraries

• Must include $ORACLE_HOME/lib

• For example:

/u01/app/oracle/product/8.0.5/lib

• Always required

$PATH

• Location of Oracle executables

• Must include $ORACLE_HOME/bin

• For example:

/u01/app/oracle/product/8.0.5/bin

• Always required

$ORACLE_SID

• Name of local Oracle instance to access

• For example: MYDB

• Overridden if application specifies Net8 alias or if $TWO_TASK is set

• Required if application does not specify Net8 alias and $TWO_TASK is not set

$TWO_TASK

• Net8 alias for local or remote Oracle instance to access

• For example: MYDB

• Overridden if application specifies Net8 alias explicitly

• Optional

$NLS_LANG

• Language and character set of client application

• Format is language_territory.CHARSETNAME

• For example: american_america.US7ASCII

• See platform-specific installation guide for a list of supported settings

• Required when default character set is not being used

$ORA_NLS33

• Location of Oracle client NLS character set data• Typically

$ORACLE_HOME/ocommon/nls/admin/data

• For example: /u01/app/oracle/product/8.0.5/ocommon/nls/admin/data

• Required when default character set is not being used

$ORACLE_BASE

• Location of OFA directory structure

• For example: /u01/app/oracle

• An optional convenience

$DBA

• Location of instance-related administrative

files

• For example: /u01/app/oracle/admin

• An optional convenience

Optimal Flexible Architecture

• A set of best practices for installing Oracle

• Developed by Oracle Consulting and refined over the years

• Observed reasonably well by the Oracle Installer

• See platform-specific administrator’s reference for complete OFA specification

OFA Guidelines

• Assigning and naming mount points

• Directory hierarchies

• Naming conventions for all files

• Naming conventions for tablespaces

• Policies for assigning segments to tablespaces

OFA Benefits• A standardized methodology

• A good naming convention

• Files organized in an easy-to-find manner

• Support for multiple databases or Oracle releases on one server

• Separation of Oracle software and database files

• Ability to distribute I/O across many physical devices

Key Directories in anOFA-Compliant Installation

• $ORACLE_BASE• $ORACLE_BASE/product/<version>• $ORACLE_BASE/admin/$ORACLE_SID

– pfile– bdump– cdump– udump– create

• <mount point>/oradata/<dbname>

Accessing an Oracle Database(as a DBA)

• SQL*Plus

• Server Manager

• Enterprise Manager

Installing Oracle

• Prepare the server

• Install the Oracle software

• Create a database

• Complete the server configuration

Our Installation Environment

• Oracle 8.0.5 Standard Edition

• Red Hat Linux 5.2

You are welcome to use other versions of Oracle or other distributions of Linux, but you may need to deviate from these steps

Oracle 8i

• Just became available in late July

• Installs very differently than Oracle 8.0.5

• Released too late to include in this presentation

Prepare the Server

1. Meet the software requirements

2. Meet the hardware requirements

3. Meet the kernel parameter requirements

4. Create a Linux group for DBAs

5. Create a software owner Linux account

6. Create mount points

7. Choose a local bin directory

Prepare the Server (continued)

8. Mount the CD ROM

9. Create the /etc/oratab file

Install the Oracle Software

1. Edit software owner’s login script

2. Log out and back in to set environment

3. Verify that TCP/IP is working

4. Ensure there is enough storage space

available

Install the Oracle Software (continued)

5. Run the Oracle Installer to install software

a. Choose a custom install

b. Choose to install software without creating a database

c. Choose a language for database messages

d. Choose the products to install

e. Choose the DBA and osoper groups

Install the Oracle Software (continued)

6. Add enhancements to the oraenv script

7. Add enhancements to the dbshut script

8. Perform certain steps as the root user

9. Double check file permissions

Create a Database

1. Choose a database block size

2. Tweak an Installer script to get the desired

block size

Create a Database (continued)3. Run the Oracle Installer to create a database

a. Choose a custom install

b. Choose to create database objects

c. Choose relevant products for database creation

d. Choose to create a filesystem-based database

e. Specify the mount point for the database

f. Choose the character sets for the database

g. Choose database passwords

h. Choose whether to load SQL*Plus help and demo

Create a Database (continued)4. Configure the Net8 listener

5. Prepare a tnsnames.ora file

6. Improve the parameter file

7. Relocate data files and redo logs to balance I/O

8. Configure the temporary tablespace

9. Configure rollback segments

10.Create application tablespaces

11.Create application schemas and roles

Complete the Server Configuration

1. Update the /etc/oratab file

2. Remove hardcoding from software owner’s login script

3. Create separate Linux accounts for database users

4. Configure automatic database start on server reboot

Managing Your Database

• Starting and stopping

• Connectivity and troubleshooting

• Schemas and users

• Tablespaces and segments

• Fault tolerance and backups

Opening and Closing a Database

• Invoking Server Manager

• Authentication

• STARTUP

• SHUTDOWN

Starting and Stopping theNet8 Listener

• Invoking the listener control tool

• START

• STOP

• RELOAD

Logs and Trace Files

• Instance alert log

• Trace files for daemons

• Trace files for server processes

• Net8 logs

Net8 Connectivity Problems

• TNS: could not resolve service name

• TNS: unable to connect to destination

• TNS: no listener

• ORACLE not available

• TNS: listener could not resolve SID given in connect descriptor

Schemas and Users

• Application owner schemas– Contain application schema objects– Not used by end users

• Individual Oracle users– Database authenticates end users– Synonyms reference application objects– Privileges to access application objects– Commonly used in client/server systems

Schemas and Users (continued)

• Generic Oracle users– Application authenticates end users– Synonyms reference application objects– Privileges to access application objects– Commonly used in web-based systems

Tablespace Functions

Tablespace Contents Name in Default Database

Data dictionary and Oracle internals SYSTEM

Rollback segments RBS

Temporary segments TEMP

Oracle and third party tools TOOLS

Unclassified user segments USERS

Application tables n/a

Application indexes n/a

Assigning Application Segmentsto Tablespaces

• Use separate tablespaces for each application

• Place tables and indexes in separate tablespaces

• Separate segments that grow or shrink rapidly from more static ones

• Separate segments that are created and dropped frequently from longer lived ones

• Give large segments their own tablespace

Segment Storage ParametersName Purpose

initial Size of the initial extent

next Size of the next extent to be allocated

pctincrease Factor by which to increase the size of eachsuccessive next extent

minextents Initial number of extents to allocate

maxextents Maximum number of extents the segment isallowed to have

pctfree Space to leave empty in each new block to allowfor updates that cause data to take up more space

pctused How much space in a block must be free beforeadditional data will be inserted

Choosing Storage Parameters For Segments to Maximize Performance and

Minimize Fragmentation

• Set the default storage clause for each tablespace as follows:

INITIAL 128k, 4m, or 128m

NEXT Same as INITIAL

MINEXTENTS 1

MAXEXTENTS 1024

PCTINCREASE 0

Choosing Storage Parameters For Segments to Maximize Performance and

Minimize Fragmentation (continued)

• When creating segments, assign them to a tablespace but do note specify storage parameters

Optimizing storage parameters was much more complicated with earlier versions of Oracle, but starting with Oracle 7.3

this task became greatly simplified.

Make Your Database Fault Tolerant

• Store multiple control files on separate devices

• Store multiple members of each online redo log group on separate devices

• Store data files on RAID filesystems

Eliminate single points of failure wherever possible.

Backing Up an Oracle Database

• Export

• Cold Backups

• Hot Backups

• Recovery Manager

Optimizing Your Database

• Tuning applications

• Sizing the SGA

• Balancing I/O

• Tuning sorts

• Configuring rollback segments

Tuning Database Applications

• Use bind variables to reduce parsing

• Tune queries so Oracle can run them efficiently– Use tools like EXPLAIN PLAN and TKPROF– Look inside the SGA while application is running

• Tune application logic to make the most of SQL and PL/SQL

Application tuning usually gives the biggest bang for the buck when optimizing Oracle systems. Reducing running time from 18 hours to ten

minutes by changing one line of code is not uncommon.

Sizing the SGA• Size the buffer cache

– Set the db_block_buffers parameter– Query v$sysstat to check hit ratio– Consider checking extended LRU statistics

• Size the shared SQL area– Set the shared_pool_size_parameter– Consider use of bind variables and PL/SQL when

sizing

Maximize cache hit ratios while keeping the entire SGA in physical memory at all times.

Balancing I/O

• Assign segments to tablespaces carefully

• Distribute data files across physical devices

• Query v$filestat to check I/O counts

• Adjust file placement as needed

Tuning Sorts

• Set sort_area_size parameter

• Assign all users a temporary tablespace

• Set content type of temporary tablespace to

TEMPORARY

• Set storage parameters on temporary

tablespace

Configuring Rollback Segments

• Lots of small segments for OLTP

• A few large segments for batch

• Usually, need to mix the two

Where To Get More Information

• Oracle documentation

• Other publications

• Oracle Technology Network

• Oracle user groups

• Free web resources

Slide Show and Tutorial Are Available in Soft Copy

Visit

http://www.dbspecialists.com/present.html

for this presentation

Contact Information

Roger Schrag

rschrag@dbspecialists.com

Database Specialists, Inc.

388 Market Street, Suite 400

San Francisco, CA 94111

415-344-0500