On Mon, 25 Mar 2013 12:28:00 -0400, Thomas David Rivers wrote: >Bill Godfrey wrote: > >>On Mon, 25 Mar 2013 09:46:56 -0400, Thomas David Rivers wrote: >> >> >> >>>I'm reworking some code to avoid multiple OPENs for >>>reading PDS members.. >>> >>>But, I will still be just reading one member at a time, >>>and I don't know the member names a-priori. >>> >>>The DFSMS documentation states that using BLDL + FIND >>>(and using the ttr,C form for FIND) results in a performance >>>improvement... over simply pointing FIND at the DCB. >>> >>> >> >>I am curious to know where the documentation says that. Can you be more >>specific? >> >> >> >Hi Bill, > > I'm looking at z/OS V1R12.0 DFSMS Using Data Sets (SC26-7410-10) >under the heading "BLDL - Construct a Directory Entry List". Paragraph >4 says: > > You can improve retrieval time by directing a subsequent FIND > macro to the BLDL list rather than to the directory to locate > the member to be processed. > > I can readily believe that statement if the BLDL list has more than > one entry... hence my question... > Thanks. That was my understanding of how the improved retrieval time would be documented. Your re-wording made me wonder if I had missed something. The sentence is referring to the difference between the 2 types of FIND after a BLDL and does not make any comparison to a FIND without a BLDL. Obviously if a BLDL list is created with multiple members, an improvement can be realized, but that's not what this sentence is about. I would expect that a FIND without a BLDL is just negligibly faster than BLDL + FIND(C) if the BLDL list is only going to have one member name, since a BLDL list is not needed.
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