Websphere App Server Tuning

WebSphere application server performance can be done in 3 levels.

1) Basic tuning 2) Advance Tuning 3) Asynchronous messaging

1) Basic Tuning includes below parameters

a) JVM Heap Size b) Thread Pool Size C) connection pool size d) Data source statement cache size
5) ORB pass by reference

a) JVM Heap Size: - Increasing JVM size permits to create more objects to be created before an allocation occurs and triggers garbage collection.Naturally this enables application to run longer period between garbage collection.Downside is increase in time to trigger garbage collection.

in order to tune the JVM heap size, verbose GC needs to be enabled. This can be done in theWebSphere Application Server administrative console by navigating to

Servers => Application servers=>server_name=> Process definition => Java Virtual Machine

. By enabling verbose GC, the JVMprints out useful information at each garbage collection, such as the amount of free and used bytes in theheap, the interval between garbage collections, and the pause time. This information is logged to thenative_stderr.log file, which can then be used by various tools to visualize the heap usage.WebSphere Application Server's default heap settings are 50 MB for the initial heap size and 256 MB for the maximum heap size. It is generally recommended to set the minimum and maximum heap sizes tothe same value for maximum performance.

One of the first items to monitor in the verbose garbage collection output is the

free heap after collection.This metric is commonly used to determine if any Java memory leaks are present within theapplication. If this metric does not reach a steady state value and continues to decrease over time, thenyou have a clear indication that a memory leak is present within the application. The free heap after collection metric can also be used in conjunction with the heap size to calculate the working set of memory (or "footprint") being used by the server and application. Simply subtract the free heap valuefrom the total heap size to get this value.