System Global Area

In the database management systems developed by the Oracle Corporation, the System Global Area (SGA) forms the part of the 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^[1]
• 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))

See also

• Program Global Area (PGA)
• User Global Area (UGA)

Further reading

• (PDF) Oracle Architectural Components

References