Memory Settings for Tomcat

By default, Tomcat sets its own memory size at around 64MB which by far this is not enough for web applications. You can set the "start size", the "maximum size" and you also need to up the heap space. to find out the proper values for your platform you will need to issue the command "java -X" in the terminal.

-Xms<size> set initial Java heap size
-Xmx<size> set maximum Java heap size
-Xss<size> set java thread stack size

Once you know your parameters you should allocate about 60% of your available Ram to Tomcat.

Linux

To set the memory you should have a file called "setenv.sh" in your /tomcat/bin directory. If the file does not exsist you should create it. Within the file set the parameters like;

export JAVA_OPTS="-Xms256m -Xmx512m"

Then restart Tomcat to apply the new settings.

Windows (started manually)

To set the memory you should have a file called "setenv.bat" in your /tomcat/bin directory. If the file does not exsist you should create it. Within the file set the parameters like;

set JAVA_OPTS="-Xms256m -Xmx512m"

Then restart Tomcat to apply the new settings.

Permanent Memory Generation

In some cases the server can run out of a different type of memory (Permanent Generation), and if this is the case the above settings may not help solve the memory issue. A problem like this may occur when running multiple applications on the same server.

If you are experiencing this type of error, you would most likely see the following error in your logs:

java.lang.OutOfMemoryError: PermGen space

To increase the level of this memory another java parameter will need to be added:

-XX:MaxPermSize=128m

Linux

As explained above all these settings take place in the setenv.sh. Add the following now;

export JAVA_OPTS="-Xms256m -Xmx512m -XX:MaxPermSize=128m"

Windows (started manually)

As explained above all these settings take place in the setenv.bat. Add the following now;

set JAVA_OPTS="-Xms256m -Xmx512m -XX:MaxPermSize=128m"

Reference URL:

Common Tomcat Memory Issues and How To Fix Them

http://wiki.apache.org/tomcat/HowTo

Additional Info:

If the JVM is using an excessive amount of memory, or spending too much time performing garbage collection, try adding this argument to get more specific information:

-verbose:gc

With this argument, the JVM periodically generates output telling you how large the Java heap size is and how much time is being spent in garbage collection.

-Xloggc:<filename>	Log GC verbose output to specified file. The verbose output is controlled by the normal verbose GC flags.
-XX:-UseGCLogFileRotation	Enabled GC log rotation, requires -Xloggc.
-XX:NumberOfGClogFiles=1	Set the number of files to use when rotating logs, must be >= 1. The rotated log files will use the following naming scheme, <filename>.0, <filename>.1, ..., <filename>.n-1.
-XX:GCLogFileSize=8K	The size of the log file at which point the log will be rotated, must be >= 8K.
XX:ParallelGCThreads=n	Sets the number of garbage collection threads in the young and old parallel garbage collectors. The default value varies with the platform on which the JVM is running.
-XX:-PrintGC	Print messages at garbage collection. Manageable.
-XX:-PrintGCDetails	Print more details at garbage collection.Manageable. (Introduced in 1.4.0.)
-XX:-PrintGCTimeStamps	Print timestamps at garbage collection. Manageable(Introduced in 1.4.0.)
-XX:-PrintConcurrentLocks	Print java.util.concurrent locks in Ctrl-Break thread dump. Manageable. (Introduced in 6.) The jstack -lcommand provides equivalent functionality.
-XX:-HeapDumpOnOutOfMemoryError	Dump heap to file when java.lang.OutOfMemoryError is thrown. Manageable. (Introduced in 1.4.2 update 12, 5.0 update 7.)