Why and when to perform this task
WebSphere for z/OS puts much higher demands on virtual memory than a traditional workload. Ensure that you don't underestimate the amount of virtual storage applied to the WebSphere for z/OS servers. Generally, they use significantly more virtual memory than traditional application servers on z/OS or OS/390. Since real storage is needed to back the virtual storage, real storage usage may also be high.Steps for this task
Note: For more information on REGION=0M and IEFUSI, please see "Preparing the base OS/390 or z/OS environment" in the Getting Started section of the information center.
If you choose to not put most of the runtime in LPA, as described in the program locations section, be sure to specify more region (as high as 512MB). Also, in conjunction with the increase in storage usage, you may have to define more paging space or auxiliary storage to back up the additional virtual storage used.
Recommendation: It can be the case that in a heavy use environment 2G of central storage is not enough to handle the real storage demands of a high volume Java application. In this case, we recommend that you configure with 64-bit real storage, which will give you the ability to dedicate more central storage to the LPAR. z/OS on a zSeries will always run in 64-bit mode. Running in 64-bit mode gives you the ability to define more than 2 GB of central storage When you configure for 64-bit real all of the storage is defined as central storage. For non-zSeries processors, or 31-bit mode, you can minimize paging by defining more expanded storage.