You are presumably using different garbage collectors. The name of the
PermGen memory area is different depending on the selected garbage collector:
-XX:+UseParallelGC : PS PermGen
-XX:+UseConcMarkSweepGC : CMS PermGen
-XX:+UseSerialGC : PermGen
Looks like Tomcat is started up with either the serial ( stop-the-world ) collector or the parallel collector.
Verify any inconsistencies in the startup scripts or the environment settings.
Update: The garbage collector and memory settings are influenced by the JVM ergonomics , which means that they get auto-selected at startup based on the characteristics of the computer the JVM is running on. I can't find any references right now but IIRC they are based on CPU architecture and total memory available.
I suggest you specify one of the garbage collectors in your startup scripts. Depending on your application, it might not be good to have a random garbage collector picked.