[Info-vax] ISAM on disk layout. Was: Re: HP wins Oracle Itanium case

[Rich Alderson]

Nomen Nescio <nobody at dizum.com> writes:

> Jan-Erik Soderholm <jan-erik.soderholm at telia.com> wrote:

>> Even more so in todays SAN's where you get a number of "gigs"
>> out of some undefined disk array. Placement of files, as in
>> MVS and other older systems, is mostly an non-issue today,

> It's a non issue today on MVS as well and has been for most of its
> history. Does anybody know if VSE still needs it?

At least as recently as _IBM z/VSE System Control Statements, Version 4
Release 3_ (SC33-8305-04, 2010), yes.

>> from a performance standpoint. The fact that MVS still needs
>> BLOCKSIZE, LRECL and so on, is mostly a compatibility issue.

> Really those are much more than just for compatibility. There are still
> millions of programs reading and writing SAM (not much ISAM, but BSAM and
> QSAM) and it helps the access method block and deliver the data. Either the
> program or the DCB has to have the information, or things will not work.

Yup.

-- 
Rich Alderson                                   news at alderson.users.panix.com
    the russet leaves of an autumn oak/inspire once again the failed poet/
    to take up his pen/and essay to place his meagre words upon the page...