heap rises and idle threads go to 0

I have a problem with a weblogic express cluster that i run.

It is a weblogic 8.1.4 3 node cluster running on RHES4.

every 2 or so days the heap size rises to 95% and then the idle threads drops to 0. then the sites become unavlable.

Any ideas where to start looking?
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AjarConnect With a Mentor Commented:
Hi willa,

    There seems to be a particular servlet/service on your website that might need cure. In order to identify this , the next time your server becomes non responsive ,open the admin console and monitor the execute queue for the non responsive server. [DOMAIN>servers>server>monitor all execute queues]It probably will turn out that most of the  threads are servicing a similiar request.  Once you have identified this request you know the part of application that is mis behaving.

    You can further get the THREAD DUMP of the server threads by  pressing Ctrl + Break on windows  and  Kill -3 <wls pid> on unix. This will get you a fair idea about the classes that are keeping the threads engaged.

It could be garbage collection gone bad...  

Do you have a dev server you can test on?  The easiest thing I can think of is to start your app on a test machine, then about 1 and 1/2 days later manually run garbage collection and see if it exhibits the same behavior while GC is running.
willa666Author Commented:
Hi  greensunie

If it is a issue with garbage collection then how can it be fixed?

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You'd need to get a really experienced coder to go over your applications on that server and look out for places where memory leaks can be caused.   Not closing database connections properly (and not using a finally clause) are a major cause of memory leaks (and can cause the GC to run early and often).  Other types of connections to other computers such as LDAP servers, other kind of authentication mechanisms, any kind of socke programming, etc.. can all cause leaks.
socke = socket
HI willa ,
Are you using any middleware ? like Tuxedo/JOLT or something like that between you app server and database.
If yes Check for the connection pool not getting released.
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