I am new to the Tomcat Administration, I have some 4 production servers running Tomcat6.x with Jdk - To monitor all my applications like Apache,Tomcat and Mysql we are using OPmanager-Application manager tool.
Intermediately i get GC critical alert. That means some times GC collection goes high and remains for more than 10 mins. Then it clears the Grabage. But this is happening recently checked all possible logs found nothing. This is not happening every time, Say like twice in a day.......
What does this data reflect? Heap usage from the JVM point of view? Memory usage from the OS point of view? I am not familiar with OPmanager so you will have to do some interpretation of the results to explain what the data means. Either way, I see nothing to be concerned with considering that the high value never even gets near 200MB.
You might also explain under what conditions OPmanger would issue a " GC critical alert". Too many GCs within a certain time period? Too many major GCs in a row? Too much heap memory used before a major GC? Too much heap memory in use after a major GC? Not knowing what the alert means makes it impossible to tell you what can be done to alleviate the problem (if there even is one).
Perhaps the trigger in OPmanager that warns about GC is not set correctly and is giving false positives. It is very likely that at some point the app deployed to Tomcat needs to gather a lot of data to do something (very possible for a monthly or yearly report, for example) and thus during that time heap usage goes up for a while until the app is done doing whatever it is doing (finishing the report, for example).
If you are really concerned about the heap usage, use a tool like jmap or VisualVM (both come with the JDK) to dump and analyze the heap. This will tell you which objects appear in abundance and give you a better idea of where to look in the app to understand what is going on.