System Global Area

System Global Area ( SGA) is called the cross-process memory areas in the main memory of the database server an Oracle database. There are all the necessary data for the instance operations.

In this storage area are located

  • Buffer Cache: This data blocks are temporarily stored, which are read from the disk. This allows the multiple access to these data blocks to be read from the cache, rather than being read from the disk again, respectively.
  • Dictionary Cache: It contains information about data dictionary tables, which include 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: Here are inter alia the most recently used SQL commands and their execution plans, as well as the dictionary cache (see above) saved.
  • JAVA pool (optional): To analyze the Java commands.
Data-Dictionary Table (database) Query plan
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