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Oracle DBA Pocket Guide
book

Oracle DBA Pocket Guide

by David C. Kreines
August 2005
Intermediate to advanced content levelIntermediate to advanced
154 pages
4h 48m
English
O'Reilly Media, Inc.
Content preview from Oracle DBA Pocket Guide
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Oracle DBA Pocket Guide
NOTE
All of the initialization parameters are described in Ora-
cle in a Nutshell and the Oracle Initialization Parameters
Pocket Reference, both from O’Reilly, as well as in the ap-
propriate Oracle documentation.
System Global Area
The System Global Area (SGA) is the shared memory area
used by the instance to store information that must be shared
between the database and the user processes. The SGA is
composed of at least three main areas: the database buffer
cache, the shared pool, and the redo log buffer. Optionally, it
may also contain the large pool and the Streams pool, if
defined. Figure 2 shows the SGA and its interaction with
other Oracle components.
Figure 2. The SGA and background processes
SGA
Database buffer
cache
Shared pool
Redo log
buffer
Large pool
DBWn CKPT LGWR ARCn
Datafiles
Control files Redo logs
SMON PMON RECO
Oracle Architecture
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Database buffer cache
The database buffer cache stores blocks of data retrieved
from the database. This buffer between the users’ requests
and the actual datafiles improves the performance of the
Oracle database. If a piece of data can be found in the buffer
cache, it can be retrieved from memory; this uses less over-
head than reading from disk. Oracle removes objects from
the cache according to a least-recently-used (LRU) algo-
rithm; ...
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Publisher Resources

ISBN: 9780596528843