On Fri, 3 May 2019 10:08:02 +0000, David Spiegel wrote: >Hi Greg, >If someone uses BLKSIZE=32760, isn't it true that only one physical >block fits on a (emulated) 3390 track, thereby definitely wasting >(2*27998)-32760=23236 bytes per track (regardless of any Program Binder >considerations)?
No, it isn't. John Eells described this in considerable detail a while ago. Look for it in the archives. For load libraries, the optimal blocksize is 32760. This is optimal both for space utilization and for performance. In many cases, it may not be better than some other blocksize, but it is never worse. The reason is that when the binder writes out w TXT record, it uses TRKBAL to determine how much space is available on the track. If necessary, it will adjust the record size so that it will use the remaining space. With a 27K blocksize, a 30K load module will always require two blocks for the TXT. With a 32K blocksize, two blocks might be required if there is not enough space at the end of the track for it. But if there is enough space on the track, that module will require only one 30K block for the TXT. -- Tom Marchant "It ain't what you don't know that gets you into trouble. It's what you know for sure that just ain't so" ---------------------------------------------------------------------- For IBM-MAIN subscribe / signoff / archive access instructions, send email to [email protected] with the message: INFO IBM-MAIN
