Consider these points when creating data sets that are used at execution time and when setting up ISPF applications.

• System-Determined Block size (SDB) should be used for the ISPxLIB data sets. To allocate a data set with SDB, code DCB=BLKSIZE=0 in JCL, or specify a block size of zero in ISPF Option 3.2 when allocating the data set. The exception to this is ISPLLIB data sets with a record format of U. These should be allocated using a block size consistent with your system conventions.
• If you do not use a system-determined block size, use a block size for the ISPxLIB data sets that is a half of a 3380/3390 track. Use a block size of 32760 for load module data sets including those allocated to ISPLLIB, if any.
• Use cached controllers for the ISPxLIB data sets.
• Use PDSEs for the ISPxLIB data sets. Pay careful attention to the parameters with which the PDSEs are defined. The direct MSR (millisecond response time) parameter of the storage class affects PDSE performance. Low values of this parameter will improve PDSE performance at the expense of increased storage use.
• Make sure the ISPxLIB data sets are on lightly used volumes. You can spread them out over multiple volumes.
• Minimize the number of ISPLLIB data sets:
  • If ISPF modules are in the LPA and LNKLIST, do not include them in ISPLLIB. It is not necessary.
  • Put commonly used ISPF applications in the LPA and LNKLIST.
  • Use LIBDEFs where possible for infrequently used applications.