W dniu 2010-04-14 19:48, McKown, John pisze:
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From: IBM Mainframe Discussion List
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Sent: Wednesday, April 14, 2010 12:13 PM
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Subject: Re: Why a VSAM VRRN vs. KSDS with 4 byte key?
W dniu 2010-04-14 16:18, McKown, John pisze:
I'm just curious as to why IBM chose to create the VRRN
type of VSAM file. I understand a normal RRN (NUMBERED). In
both cases, the record is addessed by relative record number.
But I don't really see the need for a VRRN. Why not just have
a KSDS with a 4 byte key at offset 0? Is it to remove the
relative record number from the user record?And, I guess, so
that you can't change the "record number" by updating the
key. Just curious.
What is VRRN? Do you mean RRDS with variable length records?
AFAIK it is
usually called vRRDS. In fact it *is* KSDS under the cover - it has
index, you specify freespace, etc.
Why vRRDS? Convenience? It's easier for existing apps.
BTW: In the old days there were (were = support dropped) option in
COBOL allowing "emulation" of vRRDS on KSDS. I guess it was created
before vRRDS was created. In this case you had to define KSDS you all
the utilities except the application did treat the dataset as
regular KSDS.
--
Radoslaw Skorupka
Lodz, Poland
Sorry. Yes - I meant vRRDS. And it is only convience, no other "special
functionality" which I would not get with a 4 byte key?
As far as I know - yes, it's only convenience.
--
Radoslaw Skorupka
Lodz, Poland
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