Lester, Bob wrote:
Hi Folks,I've been following this thread. We have some of 32K, some of 1/2 block. BUT, we also have 19069, 6144, etc. Can I look at the load module size to determine if the module length is greater than the load library blocksize? Is this a productive use of time?
First, let me say that IBM recommends all IBM system software load libraries be allocated at a block size of 32,760. We have never yet extended that to application load libraries and I am not doing that here. What follows is thus just my unsupported opinion:
I'd say any data set by data set analysis would not be worth your time. COPYMOD the modules to load libraries allocated at 32,760 and you will very likely save space and possibly improve performance. There is no downside I'm aware of, other than your time to do the copies, from a z/OS standpoint.
Of course, if you have some vendor or home grown code somewhere that depends on the block size, all bets are off. I've never heard of any yet but that doesn't mean there is none. And I suppose something within z/OS could come out of the woodwork but nobody has come up with one since 1997 when I originally reached this conclusion for system software data sets. This is why ServerPac allocates all load libraries at a block size of 32,760.
Whether this activity would be worthwhile "depends." It's hard to quantify the benefits in advance without that data set by data set analysis, which would take more time than the COPYMODs.
Note that 13030 and 19069 are historical maximum track lengths, for 3330, and 3350 respectively. They were good block sizes at the time for the same reasons that 32,760 is a good block size today. 6144 was chosen, IMO, due to "fixed block thinking" as a good submultiple of the track length, but full track blocking would actually have been better during the 2314/3330/3350 era.
-- John Eells z/OS Technical Marketing IBM Poughkeepsie [email protected] ---------------------------------------------------------------------- For IBM-MAIN subscribe / signoff / archive access instructions, send email to [email protected] with the message: INFO IBM-MAIN
