For normal z/VSE VSAM:
1) you can use DISP=NEW, which resets the High RBA at open if the file is defined with REUSE. 2) you can use DISP=DELETE, which resets the High RBA at close if the file is defined as REUSE. (note: Space is not released.) 3) with very limited exceptions, you always use IDCAMS to define or delete the VSAM file.
4) the default is DISP=(OLD,KEEP,KEEP) is the default.

The limited exception mentioned is when using "VSAM managed SAM files". You don't have these on z/OS. (AFAIK) I will discuss them after I discuss regular non-VSAM files.

So, for most situations, DISP= is not specified on the z/VSE DLBL card.

Tony Thigpen

Wayne Bickerdike wrote on 07/10/2018 03:52 PM:
*How can it infer the difference between KEEP and DELETE?  (Or is thatthe
"mostly" part?)-- gil*

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