Re: ancient disks, Architectural implications of locate mode I/O

John Levine wrote:

According to Stephen Fuld <SFuld@alumni.cmu.edu.invalid>:

Things would have been much better if they simply used some sort of
"table of contents" or index at the start of the PDS, read it in,
then did an in memory search.  Even on small memory machines, if
you had a small sized index block and used something like a B-tree
of them, it would have been faster.

 
I believe that's what they did with VSAM.

Agreed in the sense that VSAM replaced ISAM, but, and I am getting
beyond my depth here, I wasn't aware that PDSs used ISAM.  I had
thought they were a thing unto themselves.  Please correct me if I am
wrong.  In any event, PDSs in their original form lasted beyond the
introduction of VSAM, or the PDS search assist functionality wouldn't
have been needed.





--
 - Stephen Fuld
(e-mail address disguised to prevent spam)