JVM commands to optimize performance

The generic Java™ virtual machine (JVM) arguments are optional command-line arguments that are passed to the JVM when WebSphere® Application Server starts. The generic JVM arguments can set the timeout value for the server-side Java remote method invocation (RMI), disable explicit garbage collection, set the garbage collection policy, and specify the nursery size.

When you configure the JVM, you can specify the optional command-line arguments in the Generic JVM arguments field. To use more than one argument, enter a space between each argument.

The following generic JVM arguments can improve system performance:

-sun.rmi.dgc.ackTimeout=10000
Sets the time in milliseconds that the server-side Java RMI runtime strongly refers to a remote object. Because RMI allocates a large quantity of short-lived remote objects, a value for the sun.rmi.dgc.ackTimeout argument that is too high can prevent the garbage collection from operating efficiently, which can cause out-of-memory problems. The -sun.rmi.dgc.ackTimeout=10000 argument sets the value to 10000 (10 seconds), which can prevent out-of-memory problems.
-Xdisableexplicitgc
Disables explicit garbage collection, which prevents System.gc() calls from starting the garbage collection process.
-Xmn1024m
Sets the size of the nursery to 25% of the maximum heap size. The nursery is the area in the heap where objects are created. If you analyze the garbage collection and then adjust the heap sizes, adjust the nursery size to reflect your changes.
-Xgcpolicy:gencon
Sets the garbage collection policy to gencon garbage collection, which places objects in separate areas of the heap based on their lifetime. After objects are created in the nursery and then survive a number of garbage collections, the objects are moved to a tenured area. When objects are separated in this way, garbage collection can run more frequently in the nursery without affecting the rest of the heap, which keeps pauses to a minimum. Because Maximo® Asset Management creates many short-lived objects, set the garbage collection policy to gencon.


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