IBM introduced PDSE Member Generations almost 20 years ago and yet today many of the utilities from IBM, and other vendors, still do not fully support them. This blog is a warning if you do use them (and I'm a BIG advocate for using them).
1. Deleting a PDSE member that has has generations using TSO Delete, ISPF member list delete, IEHPROGM, etc. will result in the base (generation 0) member being deleted but will not delete any of the generations. It will, however appear that the member and generations were deleted if using TSO LISTDS MEM, all standard ISPF services, IEHLIST, etc., to display the members as those tools do not understand member generations.
2. If using PDSE Member Generations there is no JCL DD parameter, no dynamic allocation option, and no JCL EXEC option to reference a generation. Which means that if you have a Load/Object Library with generations enabled and wanted to reference a prior generation you are out of luck. Which begs the question of why support PDSE Member Generations for load modules.
There are tools that understand PDSE Member Generations - the native ISPF does if you know the 'magic' keystrokes. Several vendor, including IBM, products provide full support for working with generations (see IBM's File Manger and Data Set Commander). There are even some open-source projects that support PDSE Member Generations (unabashed plug for PDSEGEN which this author developed that can be found at https://github.com/lbdyck/pdsegen or cbttape.org in file 969. Note that none that the author is aware of support executing a prior-generation load module.
With z/OS 3.1 IBM has committed to improving the ISPF support for member generations. At this point the author does not know the extent of those improvements but we have hope.
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