System Global Area
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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))
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
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- ↑ "Memory Architecture" in Oracle Database Concepts 11g Release 1 (11.1)
- ↑ Lua error in package.lua at line 80: module 'strict' not found.
