Sunday, February 26, 2012

Heap size K exceeds notification threshold (2048K)

Memory Notification: Library Cache Object loaded into SGA
Heap size 2294K exceeds notification threshold (2048K)
These are warning messages that should not cause the program responsible for these errors to fail. They appear as a result of new event messaging mechanism and memory manager in 10g Release 2.

The meaning is that the process is just spending a lot of time in finding free memory extents during an allocate as the memory may be heavily fragmented. Fragmentation in memory is impossible to eliminate completely, however, continued messages of large allocations in memory indicate there are tuning opportunities on the application.

[ Note:- Set _kgl_large_heap_warning_threshold to a reasonable high value or zero to prevent these warning messages. Value needs to be set in bytes.
The default threshold in is 2MB. So these messages could show up frequently in some application environments.
In, the threshold was increased to 50MB after regression tests, so this should be a reasonable and recommended value.