> > APAR OA27291 describes the change in GETMAIN that was introduced in > > z/OS 2.1. It results in better performance of GETMAIN. A side > effect is that is > > that there is somewhat more chance that a request will be satisfied from a > > location that had been previously obtained and then freed. > > > Is it "more chance", or simply that the hazard is shifted to a different > sequence of GETMAINs?
As the designer and implementer of the z/OS 1.10 change, I would say that it creates some additional circumstances where a request (or part of a request) can be satisfied from a location which contains residual data from a previous use. "More chance" is may be a reasonable way to say that colloquially. But yes, the actual behavior depends entirely on the sequence of requests. There is no randomness involved. > Why does the option for "dirty" GETMAIN (I forget the correct name) remain > undocumented, despite its value for testing? IGVINITGETMAIN is the TRAP name. It was designed and implemented as a one person, unfunded, spare time project, by me, to meet some my needs for testing purposes. There were none of the design and externals reviews that are done for the normal development process of documented functions. Low implementation cost, affecting only system components in which I was sufficiently experienced to dabble (which does not in JCL converter/interpreter), was essential. Not being an officially documented function shields it somewhat from complaints about the usability of the externals, complaints about what it does and doesn't do, and requests for enhancements. Also, use of this kind of test tool can cause unexpected damaging system effects. In one case years ago, it exposed a bug which caused corruption of an HSM control data set. Even on a test system, that was pretty disruptive, and it quite a bit of effort for the ISV who encountered this misfortune, working with HSM level 2 support, to salvage his HSM environment. > Why is that option system-wide rather than being available with JOB scope > (option on the JOB statement) or job step scope (option on the EXEC statment)? > I'd use it for testing if it were available to me. See above. Or, to quote from "Man of La Mancha": Don Quixote: "We waited, sire, for a dwarf to mount the battlements... and announce us, but none appeared." Innkeeper: "The, uh, the dwarfs, they're all busy." Jim Mulder z/OS System Test IBM Corp. Poughkeepsie, NY
