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.
In general, the SGA consists of the following:
- dictionary cache: information about data dictionary tables, such as information about account, datafile, segment, extent, table and privileges
- redo log buffer: containing information about committed transactions that the database has not yet written to online redo log files
- the buffer_cache or "database buffer cache": holds copies of data blocks read from datafiles
- shared pool, the cache of parsed commonly used SQL statements, and also the data-dictionary cache containing tables, views and triggers
- Java pool, for parsing Java statements.
- large pool (including the User Global Area (UGA))
- Program Global Area (PGA)
- "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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