System Global Area
In the database management systems developed by the Oracle Corporation, the System Global Area (SGA) forms the part of the system memory (RAM) shared by all the processes belonging to a single Oracle database instance. The SGA contains all information necessary for the instance operation.
Components
In general, the SGA consists of the following:
- buffer cache: holds copies of data blocks read from datafiles[1]
- dictionary cache: holds information about data dictionary tables, such as information about account, datafile, segment, extent, table and privileges
- redo log buffer: contains information about database transactions, both committed and uncommitted, in preparation for writing to online redo log files
- shared pool: holds the dictionary or row cache, the library cache, cursor definitions and shared SQL.
- Java pool: holds information for parsing Java statements.
- large pool: including the User Global Area (UGA))
- stream pool:this is remote connectivity for the database.
- log buffer:this is cirucular ratiation and modify or change all data in database.
Configuration
From Oracle Database version 10g, Automatic Memory Management (AMM) allows simplified and dynamic configuration of the SGA.[2]
See also
- Program Global Area (PGA)
Further reading
References
- ↑ "Memory Architecture" in Oracle Database Concepts 11g Release 1 (11.1)
- ↑ Burleson, Donald K., ed. (2003). Oracle Database 10g New Features: Oracle 10g Reference for Advanced Tuning & Administration. Oracle In-Focus. Rampant TechPress. p. 22. ISBN 9780974071602. Retrieved 2012-11-22.
Oracle Database 10g [...] has Automatic Memory Management (AMM) in the form of the [...] parameter [...] sga_target, which [...] automates the allocation of RAM between the data buffers, shared pool, and log buffers.
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