For data set operations, the default method of serializing usage of data sets is to enqueue on the data set name. If the DYNALLOC keyword is coded in the control cards, the time taken to serialize is much greater than that taken by using the ENQ macro. So use DYNALLOC keyword judiciously. Use it only on a JES3 system if the interface between the allocation function and JES3 is not disabled. If the interface is disabled, then the end result of serialization using ENQ is the same as using dynamic allocation; ENQ takes much less time to serialize data sets.

When you use DYNALLOC keyword, the selected data sets are allocated to DFSMSdss. If some data sets are allocated to the system, they can only be processed by DFSMSdss with DYNALLOC if SHARE is also specified. Table 2 provides more information on data set serialization.