5. Maintenance › 5.16 SAS Configuration Options Used by CA MICS › 5.17.3 Considerations of using PDSEs with CA MICS

5.17.3 Considerations of using PDSEs with CA MICS

 Each member of a PDSE library must reside in its own 4K block
 while it physically resides on DASD.  For libraries with many
 small members, such as the CA MICS data dictionary and
 documentation libraries, (sharedprefix.MICS.DIC.TEXT and
 sharedprefix.MICS.DOC.TEXT, respectively), this results in a
 larger space requirement for these libraries.  Our own
 in-house test results reflected a 50% increase in the space
 used by the dictionary library, and a 26% space increase in
 the documentation library.
 
 Most other libraries also increased in size.  We recommend that you 
 allocate 20% more space when you reallocate/copy a CA MICS PDS to a
 PDSE library.  Although it is possible to expand a PDSE data set up
 to 123 extents, avoid fragmenting your data sets whenever possible 
 to achieve the best performance.

 When you are using ISPF to allocate a PDSE library, directory blocks
 are not required.  If you are going to use JCL to allocate the new
 PDSE library, you must specify the number of directory blocks or
 the job will fail with a JCL error.  Note that the directory block
 specification is only used if the PDSE library is being
 converted back to a PDS library.
 
 There are performance considerations associated with the use
 of a PDSE data set.  For more information, review IBM Redbook
 "Partitioned Data Set Extended Usage Guide", publication
 number SG24-6106.