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Summary
In the Oracle10g a new heap checking mechanism, together with a new messaging system is introduced. This new mechanism reports memory allocations above a threshold in the alert.log, together with a tracefile in the udump directory. If you notice in your alert.log messages like:
Memory Notification: Library Cache Object loaded into SGA
Heap size 58689K exceeds notification threshold (51200K)
then the threshold set by hidden parameter _kgl_large_heap_warning_threshold exceeded!
In certain situations it can be handy to know if large allocations are being done in the sga heap (shared pool), but only to troubleshoot memory allocation problems (which eventually will appear as the infamous ORA-4031). For normal day to day work, I doubt the effectivity of these messages.
The default limit is set at 2048K. To find the value of this parameter execute
SELECT * FROM (
SELECT a.ksppinm AS parameter,
a.ksppdesc AS description,
b.ksppstvl AS session_value,
c.ksppstvl AS instance_value
FROM x$ksppi a,
x$ksppcv b,
x$ksppsv c
WHERE a.indx = b.indx
AND a.indx = c.indx
AND a.ksppinm LIKE '/_%' ESCAPE '/'
ORDER BY a.ksppinm)
WHERE parameter IN ('_kgl_large_heap_warning_threshold')
In the description of the parameter indicates:
maximum heap size before KGL writes warnings to the alert log
Workaround
If you want to disappear the message from the alert.log increase the hidden parameter to something bigger, for example
ALTER SYSTEM SET "_kgl_large_heap_warning_threshold" = 99428800 SCOPE=SPFILE ;
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