Weblogic GC activity

Question

Hello,
We have some performance issue with our weblogic server. Upon investigation, I notice something related to GC which I am not sure is a normal behavior or not.
In the Server logs, I am seeing the following line periodically
<server name>.log00105:####<Jan 22, 2009 5:23:55 AM GMT> <Info> <Health> <host name> <server name> <weblogic.GCMonitor> <<anonymous>> <> <> <1232601835522> <BEA-310002> <10% of the total memory in the server is free>
Before our server went in to a bad state, this line was disappearing in the logs for almost 5 days.
Would like to know whether the absence of this line means the JVM did not perform the GC activity for those 5 days or is it like Weblogic not necessarily need to log this line but GC activity would be carried out by JVM periodically in the background?
Any pointers will be of great help for our investigation. Thank you.
Our server details are
OS - HP-UX
OSVersion: B.11.23
Java Vendor: Hewlett-Packard Company
Weblogic Version: WebLogic Server 9.2 MP1

Answer 1

The garbage collection cycles in the JVM and the report from the WebLogic GC Monitor are two different things. The JVM will go on executing GC cycles whether the GC Monitor runs at all. I have no idea why you wouldn't have seen this report in the logs.
Also note that if you're concerned that the free memory gets to such a low level, if you're not using a generational collector, or you end up with a very large young generation, it's perfectly natural for the free memory to get very low, just before the GC that bumps it way up to 60-70 % free.