RE: Heap size 3664K exceeds notification threshold
- From: "Hallas, John (EXP N-ARM)" <john.hallas@xxxxxxxx>
- To: JDunn@xxxxxxxxx, oracle-l@xxxxxxxxxxxxx
- Date: Fri, 13 Jul 2007 08:45:03 +0100
See note 330239.1 - some parts pasted below
HTH
John
Changes
Installed / Upgraded to 10g Release 2
Cause
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.
The messages do not imply that an ORA-4031 is about to happen.
Solution
In 10g we have a new undocumented parameter that sets the KGL heap size
warning threshold. This parameter was not present in 10gR1. Warnings
are written if heap size exceeds this threshold.
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.
If you want to set this to 8192 (8192 * 1024) and are using an spfile:
(logged in as "/ as sysdba")
SQL> alter system set "_kgl_large_heap_warning_threshold"=8388608
scope=spfile ;
SQL> shutdown immediate SQL> startup
SQL> show parameter _kgl_large_heap_warning_threshold
NAME TYPE VALUE
------------------------------------ -----------
------------------------------
_kgl_large_heap_warning_threshold integer 8388608
If using an "old-style" init parameter,
Edit the init parameter file and add
_kgl_large_heap_warning_threshold=8388608
NOTE: The default threshold in 10.2.0.1 is 2M. So these messages
could show up frequently in some application environments.
In 10.2.0.2, the threshold was increased to 50MB after regression
tests, so this should be a reasonable and recommended value. If you
continue to see the these warning messages in the alert log after
applying 10.2.0.2 or higher, an SR may be in order to investigate if you
are encountering a bug in the Shared Pool.
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