When Performance Analysis try to generate the explain plan of a query Oracle generate a trace dump of 600 Mb.
In the Oracle trace file you find:
Memory Notification: Library Cache Object loaded into SGA
Heap size 60958K exceeds notification threshold (51200K)
KGL object name :EXPLAIN PLAN /* rep_cm_sql */ SET STATEMENT_ID = '35725.381' INTO quest.QUEST_CM_PLAN_TABLE FOR select * from ( <SQL statement>)
In 10.2.0.1 Oracle introduced a new undocumented parameter that sets the KGL heap size warning threshold. This parameter was not present in 10gR1. Warnings are written to the alert.log if heap size exceeds this threshold.
NOTE: The default threshold in 10.2.0.1 is 2M, so these messages could show up frequently in some application environments. Performance Analysis has exceeded the heap size threshold and has triggered a warning message in the alert log.
Please have a look at solution sol38632: https://support.quest.com/SUPPORT/index?page=solution&id=SOL38632