set parameter _in_memory_undo = FALSE to disable IMU
Workaround: Disable IMU (set _in_memory_undo=FALSE)
PLEASE NOTE: This bug applies to single instance databases and not RAC as IMU is not enabled in RAC.
注意在RAC系统中IMU是不可用的，所以也就不必要去设置_in_memory_undo=FALSE
The workaround will prevent the problem, but will not fix it.
Note: _in_memory_undo is a dynamic parameter for 10g with values of TRUE or FALSE. It specifies whether there should be in memory undo for transactions. Setting this value to FALSE will disable this feature. This will cause excess redo generation.
_in_memory_undo is applicable when
compatibility >= 10.0
undo_management = AUTO
cluster_database = FALSE
Running IMU transactions may generate out-of-order redo records
Disabling in memory undo (_in_memory_undo=false)
can help to eliminate "In memory undo latch" contention
but there may still be "undo global data" latch contention
as that latch is used regardless of the setting of
_in_memory_undo. The fix for this bug can help reduce
contention on both latches.