On Thu, 20 Aug 2015 14:09:48 -0700, Charles Mills wrote: >cmp requires both files, right? I suspect the problem here is "is the file >different today than what it was yesterday?" > If you haven't both files, the optimization of comparing only the VTOCs and the first several records requires that those be saved.
>Interesting point on record lengths. Even RDW hashes don't actually solve the >entire (theoretical -- probably not real) problem. What about two FB files >with the same bits but different record lengths (e.g., 500 80-byte records >versus 1000 40-byte records). They are unarguably different but a hash might >yield the same sum for both. > I oversimplified here. In fact, I first converted to RECFM=V so I had RDWs. (And my antagonist on CMS-PIPELINES argued that they are practically *not* different. For some applications his view is correct.) >Is the requirement exclusively QSAM files? What about VSAM? What about PDS? >PDSE? PDS(E) as a whole or member by member? I strongly suspect that unlike >for a QSAM file, that if I overwrote a PDSE member with identical data, the >hash for the PDSE as a whole would change. > You must extract and compare what matters and ignore everything else. Some of my co-workers despise "diff" because it has no option to ignore 73-80 which they regard as (sometimes) inconsequential. Except when we deliver ++SRC subject to USERMODs. -- gil ---------------------------------------------------------------------- For IBM-MAIN subscribe / signoff / archive access instructions, send email to [email protected] with the message: INFO IBM-MAIN
