Spotlight on Oracle 10.9 - Getting Started Guide

In Memory Undo Latch Wait Alarm

The in memory undo latch is associated with Oracle's relatively new in memory undo (IMU) structures. These structures hold in memory information formerly maintained in rollback (undo) segments. Some contention might be as a result of the new algorithm reducing redo generation and undo segment IO.

Possible remedies:

• Increase the value of the PROCESSES parameter. This parameter indirectly controls the default number of IMU latches.
• Turn off memory undo by adjusting the undocumented parameter: _IN_MEMORY_UNDO

Note: Oracle Corporation recommends changing undocumented parameters ONLY at the direction of Oracle Support.