(ZOS) LE tuning tips for z/OS

Enable xplink in the runtime environment and compiling applications with xplink enabled improves performance in z/OS V1R2.

• For best performance, use the LPALSTxx parmlib member to ensure that LE and C++ runtimes are loaded into LPA, as shown in the following example:

  Example: sys1.parmlib(LPALSTxx):

  ********************************* Top of Data ********************
  USER.LPALIB,                                                      
  ISF.SISFLPA,                           	SDSF                       
  CEE.SCEELPA,
                              LANGUAGE ENVIRONMENT      
  CBC.SCLBDLL,                            C++ RUNTIME      
  .
  .
  .
  
  ******************************** Bottom of Data ******************
  
  

• Ensure that the Language Environment data sets, SCEERUN and SCEERUN2, are authorized to enable xplink.

  For processes that run the client ORB, since they start the JVM, must run with xplink (on). For best performance, compile applications that use JNI services with xplink enabled. Compiling applications with xplink enabled improves performance in z/OS V1R2. As you move from z/OS V1R2 to z/OS V1R6 we should experience additional performance improvements when all of the LE services calls are xplink enabled.

• Ensure that we are NOT using the following options during production:
  • RPTSTG(ON)
  • RPTOPTS(ON)
  • HEAPCHK(ON)

• Turn LE heappools on.

  If we are running a client on z/OS, setting the following: SET LEPARM='HEAPP(ON)' in a shell script, turns on LE heappools, which should improve the performance of the client.

• Refer to Fine tuning the LE heap

Customization Note: Do not modify LE parameters without consulting IBM support. The LE parameters are set internally to ensure the best possible performance of the WAS, which is the main LE application running in the address space. If we need to add or change LE parameters, make sure that you work with the IBM WebSphere support team to ensure that the internally set parameters are not compromised. The appropriate interface for making these changes is through the PARM= parameter of the EXEC PGM=BPXBATSL statement in the startup JCL.

Tune the z/OS operating system