Hi Peter,
Partially right
In a VSAM file (KSDS only I think) you can request the Index to have
compressed keys
Only worth while if the keys were large (max length is 127 bytes)
The Index entry would be compared to the previous and both the beginning and
ending key bytes would be compared and whatever was the same got a length
instead of the bytes, the final index entry looks horrible, but it saved
valuable disk space back in the time when dinosaurs (like me) ruled the
Earth :-) The RBA would not have been there for a KSDS
Have I got the very last "VSAM Logic" Manual on the planet ?
Melvyn Maltz
----- Original Message -----
From: "Farley, Peter x23353" <[email protected]>
To: <[email protected]>
Sent: Wednesday, March 14, 2018 10:18 PM
Subject: Re: Two string instruction questions
I think I read somewhere that is what keyed VSAM Index records are, aren't
they? A count of equal key bytes and then the remaining non-equal bytes,
followed by the RBA in the data component? Or is that a fib I was told?
Peter
-----Original Message-----
From: IBM Mainframe Assembler List [mailto:[email protected]]
On Behalf Of Charles Mills
Sent: Wednesday, March 14, 2018 5:49 PM
To: [email protected]
Subject: Re: Two string instruction questions
That's interesting. Thanks!
I did think of what CUSE would be perfect for: what I know as "vertical
compression" but Google does not seem to know the term. Think of standard
run length compression as "horizontal." Picture something like that, but
where a code indicates "the next 'n' bytes of this record are identical to
the bytes in the same position in the previous record." Only works for
sequential files, because you need the previous record to decode this
records. But works well where there are a lot of repeating fields.
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