Memory Leaks in Java

Question

Hi,
I have a considerably large business application that consists of JSPs and JavaBeans which connects to a database. The application runs off a Tomcat server. Some information about the application is as follows:
a. JDK version 1.4.2_11
b. Database used is MS SQL Server 2000 with Server pack 4
c. Running on Tomcat version 4.1.31. Tomcat is being run under services.
d. Third party libraries -
     Cryptix32
     i-Net Crystal Clear
     CeWolf and JFreeChart
     iText
     jxl
I noticed that the Tomcat memory utilization increases after a period of using the application.
I recently purchased JProbe as it was recommended as a good tool to check for memory leaks in Java applications. Having purchased Jprobe, the team is now proceeding to investigate the cause of the problem.
I would like very much to seek the expertise of the community here as to some technique / steps the team should take during the course of the investigation.
We are currently following the following steps:
a. Startup JProbe
b. Set a JProbe J2EE memory session which points to Tomcat and JDK
c. Run the JProbe session
d. Do a Collect Stack Trace
e. Login to our application, execute a "single function" and then logout
f. Do an Include Heapdump in Snapshot
g. Save the snapshot
h. Stop the JProbe session
i. Investigate the output
j. Repeat (c) to (i) for other functions in our application
Would appreciate if the community here could advice if we are proceeding with the investigation correctly and whether we are missing out on any memory leaks. All suggestions are most welcome.
Thanks.

Answer 1

Hi,
Just a bit more information about the application:
Application contains:
- 4490 JSP files
- 1492 Java Classes
Application Server:
- Tomcat 4.1.31
- JDK 1.4.2_11
Database:
- Microsoft SQL Server JDBC 2000
- Microsoft SQL Server 2000 SP4
Other JAR files:
- Cryptix 32
- jxl
- CeWolf
- i-Net Crystal Clear
All items mentioned above is running on a Server with Microsoft Windows Server 2003 with 2GB of RAM.
The JSP communicates to the JavaBean which in turn will connect to the Database via JDBC. We are not using connection pooling at the moment.
The SQL Server takes around 1GB of ram and I have configured Tomcat with an Initial 250MB and a maximum of 750MB of RAM. Tomcat is running under NT services.
Tomcat memory slowly increases and it takes around 4-7 weeks before it reaches the maximum memory and we get the out of memory error.
We have done checking for memory leaks using JProbe but have not found any leaks in our program yet. We did find some of our classes were not closing the connection. I am not sure whether this could be the cause of the memory leak. We have also checked for static members in our classes and have not found anything wrong with them.
Can anyone tell me whether:
a) Is 2GB RAM sufficient for this type of configuration?
b) If we add more RAM will it be more beneficial?
c) Our Tomcat web.xml configuration. Reloadable = true, Development = true. Will this cause memory leaks?
d) Should we upgrade to Tomcat 5 or 6?
e) Should we upgrade the JDBC Driver to 2005?
f) Should we upgrade the version of JDK to 1.5 or 1.6?
g) Is it recommended to restart Tomcat every now and then?
Thanks.