[Info-vax] Example of random access by record number on an RMS fixed record size, relative organization file?

[gah4]

On Thursday, September 21, 2023 at 2:02:39 PM UTC-7, David Jones wrote:
> On Thursday, September 21, 2023 at 2:20:44 PM UTC-4, gah4 wrote: 
 
> > > If the requirement is some type of keyed file, then just use a keyed file type. 
> > OS/360 has a keyed file type, but I believe it does a linear search. 
> > I suspect it is used for the index of ISAM.

> My recollection is that RMS indexed files are more akin to IBM VSAM file structure, 
> ISAM came earlier.

VSAM is supposed to have started with OS/VS about 1973.
That would have been in time for VMS. 

I think it was some time after 1973 by the time I first heard about it,
and even then much longer before I knew anything about it.
(Other than sounding fancy and new.)

BISAM and QISAM, the actual IBM names, depends a lot on feature
of S/360 and especially channels.  But also memory sizes increased
much from 1963 to 1973.  OS/360 could run on machines down to
about 64K bytes, though for them DOS/360 might be more usual.

Otherwise, outside IBM, ISAM seems to be a generic term for something
that might or might not be so similar.