Number of index levels is affected by data CA/CI sizes, index CA/CI
sizes and how well the key "compresses" between adjacent CIs. Until you
have a loaded file, you can't be positive about how many levels you
have. But, once you have it loaded, it's easier to make adjustments
prior to another re-load. Too many index levels usually indicate
something else is not right.
Tony Thigpen
Michael Watkins wrote on 8/30/20 9:07 PM:
More efficient in terms of fewer index LEVELs as Tony Thigpen may have been
getting at? I thought the number of LEVELs was contingent on the the size of
the file and the number of CI and CA splits the index component had endured
and not the allocation of contiguous space for the index component on DASD. A
REORG should reduce the number of LEVELs to its smallest possible number, no?
-----Original Message-----
From: IBM Mainframe Discussion List <IBM-MAIN@LISTSERV.UA.EDU> On Behalf Of
Mike Schwab
Sent: Sunday, August 30, 2020 7:48 PM
To: IBM-MAIN@LISTSERV.UA.EDU
Subject: Re: Simple VSAM question on sizing INDEX component
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CYL(4 1) should leave one cylinder empty. Cylinder CA will result is a more
efficient index.
On Sun, Aug 30, 2020 at 5:12 PM Lizette Koehler <stars...@mindspring.com> wrote:
List -
I have a VSAM Dataset that has grown over the years. When it was set
up - the INDEX space was left to default
I am wondering if it makes sense to override the Track Allocation and
put it in Cylinders.
We are noticing a little bit of an increase in run time during reorg.
I was wondering if this might be due to the data set having 3.4GB now.
This file is EA/EF so it can grow
Over 4500 Cylinders on the Data
And the index is using tracks 2 pri and 11 sec - size is now 2.4 MB
During reorg we offload records to an archive then reload the current
data back in
This may be something I cannot improve on, just thought I would see if
there are any insights I am missing.
Process:
Offload the data to a temp file
Archive records older than 2 weeks
Del/Def VSAM dataset
Reload current records to VSAM dataset
This runs daily
Thank you
Lizette
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Mike A Schwab, Springfield IL USA
Where do Forest Rangers go to get away from it all?
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