PrimePSA (EXEC PGM=IGVDGNPP) is not documented and is not supported. And that is not likely to change. It certainly won't change without a formal request for the functionality it provides. You can do what you want, and I don't recall it ever not doing what it intends to do, but do not expect assistance from IBM Service with respect to anything within your system that goes awry due to that (be it IBM code or otherwise). Running it usually exposes problems but can, actually, hide a problem depending on the instructions that are unintentionally referencing the first page.
Shmuel wrote >Would there be utility in accepting a MODIFY command to reprime with a >different value? The V= parameter (in the example V='50404143,AAAAAAAA,55555555,FFFFFF7F') identifies a group of values that are cycled through. Martin Ward's example of erroneous reference to page 0 that a scan can find (I removed the "nnnn" and "mmmmm") CLC 0(R1),field field DC C'9' is also flagged by *PROCESS FLAG(PAGE0) which had been mentioned. Many would think that it best to have such problems exposed by the assembly itself. Peter Relson z/OS Core Technology Design