Copyright Oracle Corporation, 1998. All rights reserved.

11

Oracle Architectural Components

Oracle Architectural Components

1-1-22 Copyright Oracle Corporation, 1998. All rights reserved.

ObjectivesObjectives

• Listing the structures involved in connecting a user to an Oracle server

• Listing the stages in processing a query

• Listing the stages in processing a DML statement

• Listing the stages in processing COMMITS

• Listing the structures involved in connecting a user to an Oracle server

• Listing the stages in processing a query

• Listing the stages in processing a DML statement

• Listing the stages in processing COMMITS

1-1-33 Copyright Oracle Corporation, 1998. All rights reserved.

The Oracle ServerThe Oracle Server

Server

Application/networkserver

Users

Oracle server

1-1-44 Copyright Oracle Corporation, 1998. All rights reserved.

Connecting to a DatabaseConnecting to a Database

UserUser

ClientClient ServerServerServerServer

processprocess

Oracle serverUserUserprocessprocess

1-1-55 Copyright Oracle Corporation, 1998. All rights reserved.

User ProcessUser Process

• Runs on the client machine

• Is spawned when a tool or an application is invoked

• Runs the tool or application (SQL*Plus, Server Manager, Oracle Enterprise Manager, Developer/2000)

• Includes the User Program Interface (UPI)

• Generates calls to the Oracle server

• Runs on the client machine

• Is spawned when a tool or an application is invoked

• Runs the tool or application (SQL*Plus, Server Manager, Oracle Enterprise Manager, Developer/2000)

• Includes the User Program Interface (UPI)

• Generates calls to the Oracle server

1-1-66 Copyright Oracle Corporation, 1998. All rights reserved.

Server ProcessServer Process

• Runs on the server machine (host)

• Services a single user process in the dedicated server configuration

• Uses an exclusive PGA

• Includes the Oracle Program Interface (OPI)

• Processes calls generated by the client

• Returns results to the client

• Runs on the server machine (host)

• Services a single user process in the dedicated server configuration

• Uses an exclusive PGA

• Includes the Oracle Program Interface (OPI)

• Processes calls generated by the client

• Returns results to the client

1-1-77 Copyright Oracle Corporation, 1998. All rights reserved.

Oracle InstanceOracle Instance

Background processes

An Oracle instance:

• Is a means to access an Oracle database

• Always opens one and only one database

An Oracle instance:

• Is a means to access an Oracle database

• Always opens one and only one database

Instance

SGA

1-1-88 Copyright Oracle Corporation, 1998. All rights reserved.

Oracle DatabaseOracle Database

Control files

Redo logfiles

Data filesPasswordfile

Parameterfile

Archivedlog files

Database

1-1-99 Copyright Oracle Corporation, 1998. All rights reserved.

Database

Other Key Physical StructuresOther Key Physical Structures

Archivedlog files

Passwordfile

Parameterfile

1-1-1010 Copyright Oracle Corporation, 1998. All rights reserved.

UserUserprocessprocess

ServerServerprocessprocess

Processing a QueryProcessing a Query

ParseParse

StatementStatement

OKOK

HandleHandle

ExecuteExecute

OKOK

HandleHandle

FetchFetch

ResultsResults

SELECT *

FROM emp

ORDER BY ename;

SELECT *

FROM emp

ORDER BY ename;

1-1-1111 Copyright Oracle Corporation, 1998. All rights reserved.

The Shared PoolThe Shared Pool

• Size defined by SHARED_POOL_SIZE

• Library cache contains statement text, parsed code, and an execution plan

• Data dictionary cache contains table and column definitions and privileges

• Size defined by SHARED_POOL_SIZE

• Library cache contains statement text, parsed code, and an execution plan

• Data dictionary cache contains table and column definitions and privileges

Shared pool

Librarycache

Datadictionary

cache

1-1-1212 Copyright Oracle Corporation, 1998. All rights reserved.

Database Buffer CacheDatabase Buffer Cache

• Number of buffers defined by DB_BLOCK_BUFFERS

• Size of a buffer based on DB_BLOCK_SIZE

• Stores the most recently used blocks

• Number of buffers defined by DB_BLOCK_BUFFERS

• Size of a buffer based on DB_BLOCK_SIZE

• Stores the most recently used blocks

1-1-1313 Copyright Oracle Corporation, 1998. All rights reserved.

Program Global Area (PGA)Program Global Area (PGA)

• Not shared and not writable

• Contains

– Sort area

– Session information

– Cursor state

– Stack space

• Not shared and not writable

• Contains

– Sort area

– Session information

– Cursor state

– Stack space

PGAServerServerprocessprocess

1-1-1414 Copyright Oracle Corporation, 1998. All rights reserved.

Instance

SGA Shared pool

Librarycache

Redo logbuffer

Database buffercache

Datadictionary

cache

UPDATE emp

SET sal=sal*1.1

WHERE empno=7369

UPDATE emp

SET sal=sal*1.1

WHERE empno=7369

Processing a DML StatementProcessing a DML Statement

1

ServerServerprocessprocess

Control files

Redo logfiles

Data files

Database

2

3

4

5

1-1-1515 Copyright Oracle Corporation, 1998. All rights reserved.

Rollback Segment Rollback Segment

DML DML statementstatement

Old Old imageimage

New New imageimage

Rollback Rollback segmentsegment

TableTable

1-1-1616 Copyright Oracle Corporation, 1998. All rights reserved.

Redo Log BufferRedo Log Buffer

• Size defined by LOG_BUFFER

• Records changes made through the instance

• Used sequentially

• Circular buffer

• Size defined by LOG_BUFFER

• Records changes made through the instance

• Used sequentially

• Circular buffer

1-1-1717 Copyright Oracle Corporation, 1998. All rights reserved.

Instance

SGA Shared pool

DBWR

Database buffercache

Database Writer (DBWR)Database Writer (DBWR)

Control files

Redo logfiles

Data files

1-1-1818 Copyright Oracle Corporation, 1998. All rights reserved.

Instance

SGA Shared pool

Redo logbuffer

LGWR

Log Writer (LGWR)Log Writer (LGWR)

Control files

Redo logfiles

Data files

1-1-1919 Copyright Oracle Corporation, 1998. All rights reserved.

Shared pool

Redo logbuffer

LGWR

Control files

Redo logfiles

Data files

Database

COMMIT ProcessingCOMMIT Processing

ServerServerprocessprocess

1

2UserUser

processprocess

3

Database buffercache4

SGA

Instance

1-1-2020 Copyright Oracle Corporation, 1998. All rights reserved.

Instance

SGA Shared pool

DBWR LGWR

Database

Control files

Data files Redo logfiles

UserUserprocessprocess

ServerServerprocessprocess

PGA

SummarySummary

Passwordfile

Archivedlog files

Parameterfile