WebSphere Application Server for z/OS differs from previous application servers in its use of memory. WebSphere Application Server for z/OS's implementation takes advantage of z/OS's efficient memory management, but, like many of today's newer application servers and languages, it is a large consumer of memory. You may experience some changes from your existing memory usage patterns. This section outlines changes you might need to make:
Note: WebSphere Application Server for z/OS V allows for multiple cells to run on the same system at the same time. Since only one level of WebSphere Application Server for z/OS code can reside in LPA, any WebSphere Application Server for z/OS address spaces using a different WebSphere Application Server for z/OS code level must load the code (SBBOLPA, SBBOLOAD and SBBOLD2) from STEPLIB. This is set in the WebSphere Application Server for z/OS Customization Dialog. However, the BBORTSS5 module must always run from LPA or the link list. This module is specific to WebSphere Application Server for z/OS V.
Because you are using dynamic LPA, you may run out of ECSA after an IPL if you do not increase CSA at IPL time. Add 40 MB to ECSA in support of WebSphere Application Server for z/OS. You should monitor ECSA after dynamically loading the runtime into LPA. Remember to increase the size of your CSA page data set accordingly.
Note: Do not dynamically load the runtime in the LPA in your development cell. Load the DLLs out of private memory instead of using ECSA.
If your IEFUSI exit routine limits the maximum region to a size smaller than what you need (128 MB minimum when you run from the link pack area or 168 MB minimum when you run from the link list), you will get an abend. To fix the problem, either change the IEFUSI exit routine to allow a larger default region, or change the JCL REGION= parameter to the size needed.
Your installation may limit (control) the specification of REGION=, usually through the JES2 EXIT06 exit or the JES3 IATUX03 exit. If so, relax this restriction for the WebSphere Application Server for z/OS JCL procedures.
Finally, check your TSO segment default region size and make sure it is at least 128 MB.