How To Deal With "SGA: allocation forcing component growth" Wait Events (Doc ID 1270867.1)

In this Document

Symptoms

Cause

Solution

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Applies to:

Oracle Database - Enterprise Edition - Version 10.1.0.2 and later
Information in this document applies to any platform.
***Checked for relevance on 24-Jul-2013***

Symptoms

When using Automatic Shared Memory Management (ASMM) or Automatic Memory Management (AMM)  by setting either SGA_TARGET or MEMORY_TARGET, you may see locking issues when the following event is encountered:

This may or may not be accompanied by ORA-4031 errors.

Cause

ASMM and AMM use an auto-tuning memory management scheme. With either of these architectures enabled, memory can be moved automatically between components in the SGA (such as the buffer cache and shared pool) in order to fill a memory request in one of these components.

The 'SGA: allocation forcing component growth' can occur if the SGA_TARGET or MEMORY_TARGET is set too low for the instance, and there has to be frequent moving of the memory between the components of the SGA like the shared pool and the buffer cache.

Solution

The 'SGA: allocation forcing component growth' can often be reduced by increasing the setting of either the SGA_TARGET (for an ASMM setup) or MEMORY_TARGET (for an AMM setup). Enlarging the SGA_TARGET or MEMORY_TARGET will allow for the various SGA components to grow without the need for "stealing" memory of another component.

Increasing by at least 10% would be a good starting point and it can be tuned further if needed.

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