Note_Tech

All technological notes.

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DBA - Memory: SGA

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• DBA - Memory: SGA
  • System Global Area (SGA)
  • Dynamic Performance views v$

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System Global Area (SGA)

• SGA

  • a read/write memory area
  • The server and background processes do not reside within the SGA, but exist in a separate memory space.

• Granule

  • units of contiguous memory in which all SGA components, except the redo log buffer, allocate and deallocate space.

• Granule size is platform-specific and is determined by total SGA size.

• vs Database Instance

  • SGA + BG processes
  • Each database instance has its own SGA.
  • Oracle Database automatically allocates memory for an SGA at instance startup and reclaims the memory at instance shutdown.

• vs processes

  • All server processes that execute on behalf of users can read information in the instance SGA.
  • Several processes write to the SGA during database operation.

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Dynamic Performance views v$

Views	Desc
V$SGA	SGA summary information.
V$SGAINFO	size information
V$SGASTAT	detailed information

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