Top tuning tips

The relevant sections of the administering section include these tips, as well as more information about why these tips work and what you should consider before you apply any of these tuning changes.

Top tuning tips

Get the WAS JVM right

Make sure that your JVM has the correct settings for the computer that your Jazz application is deployed on. This is one of the most frequent causes of issues in Jazz deployments. There are a series of options, and you need to set each appropriately.

• -Xmx4G - This is the maximum JVM heap setting. It should be no more than half of the available memory on the computer that hosts the Jazz application. In this example, it is set to 4 GB, which assumes that you have 8 GB of memory on the computer that hosts this Jazz application instance.
• -Xms4G - This is the minimum JVM heap setting. It should be set to the same value as the maximum JVM heap setting.
• -Xmn512M - This is the heap "nursery" setting, and this should be set to 1/8 of what your settings for the maximum and minimum JVM heap are. In some situations (usually validated by close examination of JVM garbage collection logs), this value may be increased to 1/4 the max and min JVM heap settings.
• -Xgcpolicy:gencon - This is the garbage collection policy that the JVM uses. Use "gencon", and don't make changes unless you have read about and fully understand JVM garbage collection and how it impacts the performance of the Jazz applications.
• -Xcompressedrefs - This indicates use of compressed references in the JVM. Use this setting unless explicitly told otherwise.
• -Xgc:preferredHeapBase=0x100000000 - This is the preferred base address of the heap. Use this setting unless explicitly told otherwise.

Ulimit, baby!

If you're using Linux, be sure to increase the the limit of open files and user processes:

• As a root user add the following lines to the /etc/security/limits.conf file:

* hard nofile 65536
* soft nofile 65536
* hard nproc 10000
* soft nproc 10000

• Restart the Linux system after the limits.conf file is modified.
• An individual user can increase the limits within a running shell with the following commands:

ulimit -n 65536
ulimit -u 10000

Validate the NIC settings

Double-check that your network cards and interfaces are set to full-duplex.

Related topics: Deployment web home, administering section

External links:

• IBM
• JVM garbage collection

Additional contributors: None