Reusable Attribute

All VSAM data sets created by DFM are initially reusable. A VSAM data set must be marked reusable before you can use DFM to clear any data set or write to a VSAM ESDS with the stream access method.

You can mark a data set reusable using the IDCAMS ALTER command with the REUSE parameter.

Note:

You must be a local z/OS® user to use the ALTER command. You cannot turn on the reusable attribute using DFM.
If you delete an alternate index file, you must use the ALTER command if you want to make the base reusable again. DFM does not automatically change the base ESDS or KSDS back to reusable.
These restrictions are implemented because it is possible for additional indexes to be defined on z/OS, which are not known to DFM.

Figure 1 is an example of an ALTER command that marks a data set reusable.

Figure 1. ALTER Command that Marks a Data Set Reusable

  //ALTER    JOB   ...
  //STEPA    EXEC  PGM=IDCAMS
  //SYSPRINT DD    SYSOUT=A
  //SYSIN    DD    *
             ALTER -
                VSAM.DFM.DATASET -
                REUSE
  /*

For more information, see the ALTER command in z/OS DFSMS Access Method Services Commands.