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05148 - Record deletion and index performance?

05148 - Record deletion and index performance?

ABAP Short Reference   General Data in Customer Master  
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Record deletion and index performance?

Gday Jim

We have done similar things many times, and all you should need is the 50
gig plus a little more.

The reorg comand looks after the index for you automatically, and I have
never noticed any dramatic increase in the amount of space required due to
indexes.

Just be awar if the table is large and has many indexes it increases the
time the job runs as the index will be re-run (Not sure if that is
technicaly correct).

Regards Alex Tambellini
iSeries 400 / SAP Basis Administrator
7-Eleven Stores Pty Ltd



>From: "Jim Doll" <jdollZp...>
>Reply-To: DoNotReply@consolut.eu
>To: <sap400Zm...>
>CC: "Margie Teppo" <MTEPPOZp...>
>Subject: Record deletion and index performance?
>Date: Wed, 20 Feb 2002 15:47:34 -0500
>
>I'm going to state this as clearly as I can, but I don't understand it
>completely myself:
>
>We've got an archive consultant in who initially raised the question. His
>concern is what happens when many records of a table are deleted? In the
>past (in, ...ahem... a non-AS/400 shop), he's witnessed a problem where
>many records get deleted, which fragments the corresponding index.
>Apparently, with a "fragmented index", the optimizer eventually starts
>processing sequentially. Never heard of such a thing on the AS/400, but
>I've never deleted half of a 100GB table before, either! (Working on COEP,
>by the way, in a 4.6C environment.)
>
>Related question: assuming that we delete half of a 100GB table and try to
>organize it. I see three choices:
>
>1 - OS/400 reorganizes it in place--pretty dangerous, probably not done
>2 - OS/400 copies everything out, and copies only the good stuff
>back--seems inefficient
>3 - OS/400 copies just the good stuff out, then renames tables
>
>If I had to guess, I would think it follows #3. My question comes down to
>this: if I'm reorganizing a 100GB table that's got half of the records
>deleted, what do I need for free space in order to reorganize--100GB or
>50GB?
>
>Thanks for any replies!
>
>Jim Doll, Perrigo SAP Technical Support
>




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