Gil, They're not really virtualized. They are encpsulated.
Ron Sent via the Samsung Galaxy Note® 8.0, an AT&T 4G LTE tablet -------- Original message -------- From: Paul Gilmartin <[email protected]> Date: 12/07/2013 09:49 (GMT-08:00) To: [email protected] Subject: Re: [IBM-MAIN] Something to Think About - Optimal PDS Blocking On Sat, 7 Dec 2013 01:56:56 +0000, DASDBILL2 wrote: >We can calculate the wasted space given the block size, average number of >blocks per track, average number of this, that, and the other thing, but >wasted space is meaningless and unknowable unless you are using a SLED 3390 >which means now at least 15, maybe 20-year old disk drives. With the advent >of RAID, the interrecord gaps have been virtualized. > If gaps and other unused space are virtualized, there is no reason for SDB ever to choose a BLKSIZE other than 32760 (or nearest multiple of LRECL). I suspect there are various implementations of RAID: some may virtualize unused space; others keep images of entire tracks, however sparsely used. I tried the experiment I suggested: I created 10 mebers of 350 records. With RECFM=FB,LRECL=80,BLKSIZE=27920 (chosen by SDB) the data set used 10 tracks. When I forced to BLKSIZE=24000, it used 7 tracks. Admittedly a deliberate worst case. -- gil ---------------------------------------------------------------------- For IBM-MAIN subscribe / signoff / archive access instructions, send email to [email protected] with the message: INFO IBM-MAIN ---------------------------------------------------------------------- For IBM-MAIN subscribe / signoff / archive access instructions, send email to [email protected] with the message: INFO IBM-MAIN
