JVM Tuning

Using the largest possible heap size will result in optimal JVM performance for UA 8.0. Heap sizes equal to or greater than 4GB are highly recommend for installations with expected user loads exceeding 250 concurrent users. To implement the appropriate heap sizes for UA 8.0, the JVM options below should be added to the SYBASE/tomcat/bin/catalina.bat file using set. These options should be set to the JAVA_OPTS variable. For example, set JAVA_OPTS=-Xms3g. The values given are for example only and should not be taken as suggestions; best values for your application will vary and should be set by measurement.

If the memory available for the JVM heap is equal to or less than 4GB the following options should be used to define the minimum and maximum heap size.

-Xms3g -Xmx3g

Starting a heap with the same minimum and maximum sizes will result in the JVM spending less time attempting to adjust the heap in response to load, and will often improve startup time.

This example sets the minimum and maximum total heap size to 3GB. The ‘g’ suffix may be replaced by ‘m’ to measure in megabytes.
If the memory available for the JVM heap exceeds 4GB the following option should be used,

-XX:+AggressiveHeap

This option instructs the JVM to push memory use to the limit: the overall heap is 3900MB, the new generation is 3072MB, the allocation area of each thread is 256KB, and the collection policy defers as long as possible before collecting. This option should be used with caution. In some cases -Xss can be used to define a smaller thread stack size.