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Oracle Architecture

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Oracle Architecture Powered By Docstoc
					Oracle Architecture

Anatomy of a Query
User Submits query updates PGA session information

Sort, hash, merge area

PGA
query

User-Server Process

continued on next page

query (from User Server Process)

Anatomy of a Query (Part 2)
no
syntactically valid? Shared SQL cache

yes
Error to user yes
execution tree exists? Data Dictionary cache Data Dictionary

no no
tables and columns exist?

yes
Data Buffer cache
Table Space

Oracle-Server instance
Retrieves results

SGA continued

Anatomy of a Query (part 3)
continued from previous page
Retrieved results session information

yes
Sort required

Sort, hash, merge area

no Results to user
Final results

PGA

Oracle-Server instance

SGA Allocating Space
Database Buffer Cache Keep Buffer Pool Recycle Buffer Pool Shared Pool

Reserved Pool
Library Cache

Database Buffer Cache Database Buffer Cache Data Dictionary Cache Shared SQL Area

Large Pool
PL/SQL procedures and packages

Java Pool Control Structures Streams Pool Redo log Buffer Cache Fixed SGA

Undo (Standard)
Updates A B C A D SGA DB Buffer Cache

A
B C D E F G DATABASE UNDO FILE

B C
A E C E

Undo (Standard)
Updates A B C A D SGA DB Buffer Cache

C’’’
A’’’ E’’

A’’
B’’ C’ D’ A B C D E UNDO FILE E F G DATABASE

B C
A E C E

Undo (Deferred Updating)
Updates A B C A D SGA DB Buffer Cache

A
B C D E F G DATABASE UNDO FILE

B C
A E C E

Undo (Deferred Updating)
Updates A B C A D SGA DB Buffer Cache

C’’’
A’’’ E’’

A
B C D B’ C’ A’’ D’ UNDO FILE E F G DATABASE

B C
A E C E

Undo (Standard)
Updates B A B F G SGA DB Buffer Cache

A
B C D E F G DATABASE UNDO FILE

B F
G A B G

Undo (Deferred Updating)
Updates B A B F G SGA DB Buffer Cache

A
B C D E F G DATABASE UNDO FILE

B F
G A B G


				
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