Less01 DBA1 New

8/2/2019 Less01 DBA1 New

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Copyright 2007, Oracle. All rights reserved.

Exploring the Oracle Database Architecture


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Copyright 2007, Oracle. All rights reserved.1 - 2

Objectives

After completing this lesson, you should be able to: List the major architectural components of Oracle

Database

Explain the memory structures

Describe the background processes Correlate the logical and physical storage structures


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Oracle Database

The Oracle relational database management system(RDBMS) provides an open, comprehensive, integratedapproach to information management


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Connecting to a Server

Client Middle tier Server

Multitier architecture shown


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Database

Data filesOnline redo

log files

Controlfiles

Oracle Database Architecture: Overview

Databasebuffercache

Shared pool

Data dictionary

cache

Librarycache

PMONSMON Others

Serverprocess

PGA

Archivedlog files

Userprocess

Instance

RECO

ARCn

SGA

DBWn

Redo logbuffer

LGWRCKPT


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Connecting to the Database

Connection: Communication between a user processand an instance

Session: Specific connection of a user to an instancethrough a user process

SQL> Select

Session

Connection

User

User

process

Server

process

Session


7/25Copyright 2007, Oracle. All rights reserved.1 - 8

Interacting with an Oracle Database

User

Databasebuffercache

Shared pool

Data dictionarycache

Librarycache

PMONSMON Others

Instance

RECOARCn

SGA

DBWn

Redo logbuffer

LGWRCKPT

Userprocess Serverprocess



Database

Oracle Database Server Structures

PMONSMON Others

Data filesOnline redo

log filesControl

files

Instance

RECOARCnDBWn LGWRCKPT

Storage structures

Userprocess

Serverprocess

Memory structures

Processes

Databasebuffercache

Shared pool


Librarycache

SGA

Redo logbuffer



Database Buffer Cache

Is part of the SGA Holds copies of data blocks that are read from data files

Is shared by all concurrent users

PMONSMON Others

Instance


Database

buffercache

Shared pool


Librarycache

SGA

Redo log

buffer



Shared Pool

Is a portion of the SGA Contains:

Library cache

Shared SQL area

Data dictionary cache Control structures

PMONSMON Others

Instance


SharedSQL area

Librarycache


Other

Databasebuffercache

Shared pool


Library

cache

SGA

Redo logbuffer



Database Writer Process (DBWn)

Writes modified (dirty) buffers in the database buffer cacheto disk:

Asynchronously while performing other processing

Periodically to advance the checkpoint

Database buffercache

Database writerprocess

Data files

DBWn



LogWriter Process (LGWR)

Writes the redo log buffer to a redo log file on disk Writes:

When a user process commits a transaction

When the redo log buffer is one-third full

Before a DBWnprocess writes modified buffers to disk

Redo log buffer LogWriter process Redo log files

LGWR



Checkpoint Process (CKPT)

Records checkpoint information in Control file

Each data file header

Checkpointprocess

Data files

Control fileCKPT



System Monitor Process (SMON)

Performs recovery at instance startup Cleans up unused temporary segments

Instance

Temporarysegment

System Monitorprocess

SMON



Process Monitor Process (PMON)

Performs process recovery when a user process fails Cleans up the database buffer cache

Frees resources that are used by the user process

Monitors sessions for idle session timeout

Dynamically registers database services with listeners

Process Monitorprocess

Database buffercache

Failed userprocess

UserPMON



Archiver Processes (ARCn)

Copy redo log files to a designated storage device aftera log switch has occurred

Can collect transaction redo data and transmit that datato standby destinations

Archiver process Archive destinationCopies of redo logfiles

ARCn



Other Processes

MMON: Performs manageability-related backgroundtasks

MMNL: Performs frequent and lightweightmanageability-related tasks

MMAN: Performs automatic memory management tasks CJQ0: Runs user jobs used in batch processing

QMNx: Monitors the Streams Advanced Queuingmessage queues



Database Storage Architecture

Online redo log files

Password file

Parameter file Archived redo log

files

Control files Data files

Alert log and trace files

Backup files

DB structures- Memory- ProcessStorage



Logical and Physical Database Structures

Database

Logical Physical

Tablespace Data file

OS block

Segment

Extent

Oracle datablock

Schema



Tablespaces and Data Files

Tablespaces consist of one or more data files. Data files belong to only one tablespace.

USERS tablespace

Data file 1 Data file 2



SYSTEMand SYSAUX Tablespaces

The SYSTEMand SYSAUX tablespaces are mandatorytablespaces that are created at the time of databasecreation. They must be online.

The SYSTEMtablespace is used for core functionality

(for example, data dictionary tables).

The auxiliary SYSAUX tablespace is used for additional

database components (such as the Enterprise ManagerRepository).



Segments, Extents, and Blocks

Segments exist in a tablespace. Segments are collections of extents.

Extents are collections of data blocks.

Data blocks are mapped to disk blocks.

Segment Extents Datablocks

Diskblocks



Database Architecture:Summary of Structural Components

Memory structures: System Global Area (SGA): Database buffer cache, redo

buffer, and various pools

Program Global Area (PGA)

Process structures:

User process and server process

Background processes: SMON, PMON, DBWn, CKPT,LGWR, ARCn, and so on

Storage structures:

Logical: Database, schema, tablespace, segment, extent,and Oracle block

Physical: Data files, control files, and redo log files



Summary

In this lesson, you should have learned how to: List the major architectural components of Oracle

Database

Explain the memory structures

Describe the background processes Correlate the logical and physical storage structures


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Practice 1: Overview

This is a paper practice with questions about: Database architecture

Memory

Processes

File structures

Less01 DBA1 New

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