System Global Area
System Global Area ( SGA ) is the name given to the cross-process memory areas in the main memory of the database server of an Oracle database . All the necessary data for the instance operations are located there.
This memory area contains
- Buffer Cache: Data blocks that are read from the disk are temporarily stored here. This makes it possible to read data blocks from the cache when accessing data blocks several times, instead of reading them again from the disk.
- Dictionary cache: It contains information about data dictionary tables, including information about user accounts, database files, segments, extents, tables and rights (privileges).
- Redo Log Buffer: It contains information about completed transactions that have not yet been written to the online redo log files .
- Shared pool: a. the last used SQL commands and their execution plans as well as the dictionary cache (see above) are saved.
- JAVA Pool (optional): For analyzing the Java commands.