Linux server problem-help me

[e99darshi]

we have two linux servers which are installed apache tomcat . one is running with the data base One is running with a java application. More than 100 users are connected to the servers.
Server machines are quad core normal PC's which are having 4 GB memory. It was running properly for last 6 months & suddenely a problem came with a slowness in application.
Suddenely java application is getting stucked & users cannot work for some time. There's no network issue also.
I am trying to identify the reason for this whether the machine problem or the problem is in the java application. Any body can help me for this?

[Rubberman]

Java is notorious for its garbage collector causing serious "drop outs" in operation when it is running. Basically, when it is reclaiming memory, the running java application will be placed "on hold". This is exascerbated when a lot of that memory has been swapped to disc. There are ways to reduce the impact of this, but it depends upon whether or not you have access to the server's java source code, and how much re-architecting your application code to utilize more recent improvements to the Java garbage collection functions that you are willing and/or able to make.