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Memory Structures and Processes

Oracle Performance Monitoring: Memory Structures and Processes

Ensure that your Oracle memory structures are adequately sized.

The Oracle database consists of an instance and data storage. The instance is a set of operating system processes and memory structures that interact with the storage. System Global Area (SGA) and Process Global Area (PGA) are two kinds of memory structures that Oracle uses.

Each Oracle instance uses SGA, which is a shared memory area, to store its data and control information for cached data blocks and shared SQL areas. The PGA, on the other hand, is a memory area that stores data and controls information for a single process and holds information about user sessions, session variables, sorts, bind variables, and so on.

As the workloads change, memory is redistributed to ensure optimal performance. How do you know if Oracle memory structures, such as the SGA and PGA, are adequately sized?

Applications Manager helps you in tracking SGA performance and the Oracle processes using PGA and the resource limit for processes. This gives you insight into how loaded your Oracle Database is and lets you determine how to distribute memory optimally among the components.

You can view historical information about:

  • SGA Performance details and statuses of the buffer cache, shared pool and redo mechanisms.
  • Dynamic PGA memory usage by named component categories for each process as well as the used, allocated and total freeable PGA memory
Monitor Oracle PGA memory usage
Monitor Oracle SGA performance

Oracle SGA and PGA Monitoring Metrics

Some of the metrics for memory structure management are as follows:

  • PGA used
  • Total PGA allocated
  • Maximum PGA allocated
  • Total freeable PGA
  • PGA freed back to OS
  • Cache hit percentage
  • Resource being used by processes
  • Buffer, Library and Data Dictionary Cache Size
  • RedoLog Buffer Size
  • Shared Pool Size
  • SQL Area Size and more

Related Oracle Monitoring Capability

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