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   '-DYNALloc-'   

DYNALLOC specifies dynamic allocation, instead of enqueue, to serialize the use of data sets. The data sets whose extents are relocated are serialized throughout the DEFRAG operation. This allows cross-system serialization with the following considerations:

• The serialization is of value only when the dynamic allocation/JES3 interface is not disabled.
• Run time increases when you use the DYNALLOC keyword to serialize data sets (as opposed to enqueue) because overhead is involved in dynamic allocation and serialization across multiple processors.
• If you are running on a system using JES3 with MDS enabled and are not using multisystem GRS (or an equivalent function), you can use the DEFRAG command DYNALLOC keyword to provide serialization for data sets on shared DASD. However, not all data sets allocated within a JES3 environment are known to the global. The following are two cases where the use of the DYNALLOC keyword does not provide cross-system serialization for these data sets:
  • Allocation of existing (old) data sets whose names appear in the RESDSN and DYNALDSN lists are not protected by the DYNALLOC serialization mechanism of DFSMSdss. You can prevent DEFRAG processing for these data sets by placing their names (or filters for the names) in the EXCLUDE list for the DEFRAG command.
  • New data sets created with nonspecific allocation (no volume serial supplied) are not protected by the DYNALLOC serialization mechanism of DFSMSdss. However, you can use BY filtering with the DEFRAG command to specifically include or exclude data sets from processing.