Java Memory Configuration ITSAR

April 14, 2014 at 5:22 PM

Are there limitations related to the Java memory configuration in ITSAR ?

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Re: Java Memory Configuration ITSAR

April 14, 2014 at 5:35 PM
There are several variables that we need to consider when changing "JAVA_OPTS" in "$TQHOME/itsar/bin/setenv.sh":

1. For 32-bit machine, a good rule of thumb is to use 1/4 of the physical memory. Since a 32-bit machine can only address up to 4GB of memory, Java
maximum heap can be assigned up to 1GB of memory. Although in UNIX, you can have up to 2GB of memory for the JVM.

2. For 64-bit machine, this setting is more complicated because theoretically you can assign more than 4GB of memory. Although the 1/4 of the total memory rule of thumb still applies, you don't want to allocate too much memory to JVM than how much it needs because the extra space is then wasted. In addition to this, ITSAR 11.1 is packaged with 32-bit Java which theoretically can't address beyond 4G. Starting as of ITSAR 11.2 64-bit Java is packaged to Linux and Windows while Solaris remains as 32-bit.

For this reason, you may allocate bigger than 4GB to Java in ITSAR 11.2 running on Windows or Linux. The default maximum value for Java heap in "JAVA_OPT" is "-Xmx512m". If there is a need to increase this maximum like when you are getting "OutOfMemoryError: Java heap space" then it is recommended to increase the maximum to "-Xmx1024", "-Xmx2048m", and so on... You may want to add also the memory start "-Xms512m". A good rule of thumb for "-Xms" is 1/2 of "-Xmx". 512m is recommended for "-Xms" but more than 2048m is probably overkill.

Furthermore, there is another limiting factor as to the maximum space per process that a process can address. For more information about this please refer to:http://docs.oracle.com/cd/E19159-01/819-3681/abeii/index.html....