Hi, because FBID order takes precedence over priority. Hence, if a user issues 1000 NOWAIT type recalls and there is a single WAIT type recall at the end of the same tape, then the Wait-type is going to be delayed until all of the NOWAIT type recalls are processed.
The introduction of the serpentine read/write technology for tapes removed the advantage of processing in FBID order for random recalls. In fact, in can make performance worse because two close FBIDs are not necessarily physically close on a tape written 'serpentinely'. Performance Tests have shown that with random recalls, processing in FBID order does not necessarily drive better performance. Hence, it is generally better to process in priority order (Wait / Nowait) than FBID. The exception is when you know that you will have Many recalls from the same tape. In that case, processing in FBID can provide a significant performance improvement. We added this support for a particular customer had a Use Case where they would recall every data set off of a tape, for which processing in FBID order provided Significant Value. That said, this is a 'recommendation'. Since each environment is unique, it would be worthwhile to experiment with the setting in your environment. Glenn Wilcock DFSMShsm Architect ---------------------------------------------------------------------- For IBM-MAIN subscribe / signoff / archive access instructions, send email to [email protected] with the message: INFO IBM-MAIN
