General comment about LBI, large blocks and performance:
1. Blocksize for tapes, especially for real tapes is very important for performance. LBI is something to legalize previously used large blocks - I mean blocks larger than officially supported 32760. Even 3490E tapes supported larger blocks and it was used by ADRDSSU (read HSM backups). AFAIK LBI was proviced with OS/390 V2R10, long time after MAGSTAR family GA.
2. Blocksize on DASD *does affect performance*, but it is not so strong as with tapes. More: on tape there is no big reason not to use large blocks, but on DASD the blocksize is strictly related to track size. For 3390 blocksize of, let's imagine 160kB has no sense, because block has to fit in track. And even 32760 is not very reasonable (assuming same consecutive blocks), because waste of space. Yes, it would be nice to have blocksize limit at 56664B, but there is no such option (we talk about z/OS, not z/VSE). Optimal blocksize is SDB, which is usually close to half of the track (sometimes third...).
3. However "big enough" blocksize is good enough! In other words you will not observe big performance difference between BLKSIZE=32000 and BLKSIZE=8000. On DASD, of course.
4. So, in this case, hypothetical LBI=track would not provide important relief. That could mean maybe there are other ways to skin a cat. I don't know the application, but some ideas to consider:
- use VSAM, SMB, BLSR, etc. - use index if applicable - use LDS and DIV - use DB2 table My €0,02 -- Radoslaw Skorupka (looking for new job) Lodz, Poland ---------------------------------------------------------------------- For IBM-MAIN subscribe / signoff / archive access instructions, send email to lists...@listserv.ua.edu with the message: INFO IBM-MAIN
