How do I set the maximum heap size for WebSphere?
There are no search results at this time.You can use one of the other support options on this page.
One of the most frequently asked questions is, "What is the maximum heap size?"" OutofMemory" condition is one of the most common problems reported in WebSphere Java support.It is not intended to be a solution for every situation, but a general set of starting recommendations.You will need to test appropriate values in your environments based on application architecture, number of applications running, how busy the App server is and underlying load conditions.For 32 bit platforms and Java stacks in general, the recommended maximum heap range is between1024M - 1536M or 1G - 1.5G; higher values will most likely eventually result in Native Memory contention.Depending on how many applications are deployed, you can use less heap memory between 512M and 1G.In most use-case scenarios, the Default out-of-the-box configuration value is probably too low.The WAS Java process shares a 4 Gigabyte memory address space with the OS in accordance with a 32 bit design specification.For 64 bit platforms and Java stacks in general, the recommended maximum heap range is between 4096M - 8192M.Depending on how many applications are deployed, you can use less heap memory.The WAS Java process shares a 16 Terabyte memory address space with the OS in accordance with a 64 bit design specification.The newer product versions WAS v8.x and v9.x with default GC Policy of GENCON, setting has been found.The Generic JVM argument of -Xmn####m can be used to fix the nursery size.The nursery region defaults to 25% of the max heap size, but it is variable and not fixed.The overhead of the GENCON GC Policy resizing heap regions makes GC very inefficient, even though the concept was to keep them smaller for faster GC cycles.To find the right area to set -Xmn, look at "Setting generic JVM arguments in WebSphere Application server."Depending on the actual product version of WebSphere, the Heap values can be set in a number of ways.It is important to keep in mind that the overall WAS JVM Process Size or Memory Footprint will typically be larger than the maximum java heap size.This entry was created for WebSphere Base and Network deployment full version products.
One of the most frequently asked questions is, "What is the maximum heap size?"
" OutofMemory" condition is one of the most common problems reported in WebSphere Java support.
It is not intended to be a solution for every situation, but a general set of starting recommendations.
You will need to test appropriate values in your environments based on application architecture, number of applications running, how busy the App server is and underlying load conditions.
For 32 bit platforms and Java stacks in general, the recommended maximum heap range is between1024M - 1536M or 1G - 1.5G; higher values will most likely eventually result in Native Memory contention.Depending on how many applications are deployed, you can use less heap memory between 512M and 1G.In most use-case scenarios, the Default out-of-the-box configuration value is probably too low.
The WAS Java process shares a 4 Gigabyte memory address space with the OS in accordance with a 32 bit design specification.
For 64 bit platforms and Java stacks in general, the recommended maximum heap range is between 4096M - 8192M.Depending on how many applications are deployed, you can use less heap memory.
The WAS Java process shares a 16 Terabyte memory address space with the OS in accordance with a 64 bit design specification.
When using the newer product versions WAS v8.x and v9.x with default GC Policy of GENCON, we found that setting a 'Fixed Heap' works and performs best, as well as a fixed nursery.The Generic JVM argument of -Xmn####m can be used to fix the nursery size.The nursery region defaults to 25% of the max heap size, but it is variable and not fixed.The overhead of the GENCON GC Policy resizing heap regions makes GC very inefficient, even though the concept was to keep them smaller for faster GC cycles.To find the right area to set -Xmn, look at "Setting generic JVM arguments in WebSphere Application server."
Depending on the actual product version of WebSphere, the Heap values can be set in a number of ways.
It is important to keep in mind that the overall WAS JVM Process Size or Memory Footprint will typically be larger than the maximum java heap size.For example: