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05159 - Creating indexes to improve performance...

05159 - Creating indexes to improve performance...

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Creating indexes to improve performance...


The answer is: it depends.
If you are running a fair number of reports against a table, it makes sense
to add an appropriate index. If you have multiple queries against a
file, often an index can be created that can be used to satisfy more than
one query.


For example, you have a query :
Select a,b,c from R3sidData/table1 where a=1, b=2, c=3.
If you only have an IX over "a,b", the DB can get you all of the rows
that match correctly for a,b. But if you still have 10K rows where c=5
and only 1 row with c=3, you will look at 10,001 rows to get the one you
want.
If you have an IX over "a,b,c", the one row is quickly found in the index,
and disk IO is greatly minimized.

Adding a single index to a table usually won't cause a significant
performance reduction, and it's easy enough to drop the ix should you
notice any slowdown...so I'd recommend trying it. Make sure you know what
the performance looks like before you add the ix, so you can truly notice
the difference on the ins/upd/delete jobs, not just your query time.

Regards, Ron

Ron Schmerbauch 507-253-4880 rschmerbZu...
iSeries 400 - ERP Development - Rochester, MN



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| | 02/20/2002 10:23 |
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| Subject: RE: Creating indexes to improve
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That was one of our concerns when we added the index. We have been
monitoring our jobs and the performance looks fine except for a couple of
jobs. One of the job's run time actually doubles, but that is a batch job
that runs once a day. The 30-min report will be run more than 50+ times
every morning.

akl.
Business Solutions Division
United Overseas Bank
Ang.KiamLianZU...
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-----Original Message-----
From: desmond_olwageZg...
[mailto:desmond_olwageZg...]
Sent: Tuesday, February 19, 2002 3:09 PM
To: sap400Zm...
Subject: Creating indexes to improve performance...


Hi, guys.

I have seen several messages regarding the creation of an index to improve
runtime. The example was improving runtime from 30 minutes to 10 seconds by
creating an index.

I approached our ABAP programmers with this info and their reaction was
that they are hesitant to create indexes because of other performance
problems that they might be creating. For example, they could create an
index on the billing table(s) to improve runtime on queries done there, but
that, by doing so, they may increase the runtime on the actual billing
process (system having to update in more places). Is this the case? Can
anyone enlighten me here please?

Thanks.

Des Olwage
Snr. Systems Administrator
Goodyear South Africa
Tel. +27 41 5055441
Cell. +27 82 824 6900




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