--- On Fri, 3/27/09, Patrick O'Keefe <[email protected]> wrote:
> From: Patrick O'Keefe <[email protected]> > Subject: Re: Optimal Tape Blocksize > To: [email protected] > Date: Friday, March 27, 2009, 5:12 PM > On Fri, 27 Mar 2009 14:54:51 -0400, > Bill Fairchild > <[email protected]> > wrote: > > >... > >In 1982 I attended a SHARE session in New Orleans in > which the IBM > presenter said that he had surveyed a huge number of data > sets in an > internal IBM development data center, and had found that > the single > most commonly used block size was 80 bytes. > Presumably many of > these people had been developing mainframe code since the > early > 1960s when S/360 began being built. > >... > > It would be nice if such things were in the distant > past. As recently > as 5 years ago I say some Program Directories specifying > block sizes > of 3120 and 6144. > > Worse yet, just a few weeks ago we were told to > allocate a trace > dataset (for an IBM product) with RECFM VB, LRECL 1024, and > > BLKSIZE 6144. (Obviously the product's own flavor of > trace; not > GTF or CTRACE.) 6144! This came from the > product's lvl2 support > team. Did they know that this was needed for a very > poorly written > trace furntion? Or did they just pick a > cherished (now thoroughly > meaningless) blksize from the distant > past? Either way, it did not > inspire confidence. > > Pat O'Keefe Pat: That *MAY* have been our IBM SE at the time Jim Garner. He was published in an orange manual. I do not think I have it anymore and I forgot to get him to sign it. The other big thing (IIRC) was not only blocksize was important but using 5 buffers (instead of 2 which was the default at the time (that were several charts in the manual showing optimal trade offs). Since its been so long ago my memory could be off at the time but shortly after he was published SAMe came along. We found a few (chuckle) issues in it and we were almost always running GTF to try and find the bugs. I think (IIRC) we got at least 10 APARS out of SAMe. We had many many tape drives and many disk drives as well. The amount of I/O is truly scary at any point in time. SAMe (IIRC) cost $85 a month at the time and it was a savior (to us) we cut our elapsed time down quite a bit but at the same time it cost storage so it was about equal. The support we got out of IBM was world class, I think we should have gotten it for free myself:) Ed ---------------------------------------------------------------------- For IBM-MAIN subscribe / signoff / archive access instructions, send email to [email protected] with the message: GET IBM-MAIN INFO Search the archives at http://bama.ua.edu/archives/ibm-main.html
