RE: SQL Performance issues questions

I'm not sure what your sql looks like but make sure you are only bringing in the columns you need if you are not already.


Thanks,
Tommy Holden

-----Original Message-----
From: MIDRANGE-L [mailto:midrange-l-bounces@xxxxxxxxxxxx] On Behalf Of Birgitta Hauser
Sent: Thursday, November 30, 2017 9:03 AM
To: 'Midrange Systems Technical Discussion' <midrange-l@xxxxxxxxxxxx>
Subject: RE: SQL Performance issues questions

Since a view never has an access path, an additional view will not have any issues on the performance.
For analyzing your SQL statement I'd suggest to use the analyzing tools in ACS or Client Access. PRTSQLINF is outdated.
Without knowing anything else, i.e. how the query looks like how many rows are in your tables, which access path (Indexes and logical files) are available, it is not possible to suggest anything.
For indexing strategies look at the white paper from Kent Milligan and Mike Caine - Indexing and Statistics Strategies.

Mit freundlichen Grüßen / Best regards

Birgitta Hauser

"Shoot for the moon, even if you miss, you'll land among the stars." (Les
Brown)
"If you think education is expensive, try ignorance." (Derek Bok) "What is worse than training your staff and losing them? Not training them and keeping them!"
"Train people well enough so they can leave, treat them well enough so they don't want to." (Richard Branson)


-----Original Message-----
From: MIDRANGE-L [mailto:midrange-l-bounces@xxxxxxxxxxxx] On Behalf Of a4g atl
Sent: Donnerstag, 30. November 2017 15:43
To: midrange-l@xxxxxxxxxxxx
Subject: SQL Performance issues questions

I have a few programs that are retrieving data from files with approximately
5 to 750 million records.

The program is executing in approximately 15 seconds which in itself is not bad. However, I would like to improve the performance by processing less records.

A logical file may provide better performance but I would not like to use a logical. I have a simple SELECT with JOIN retrieving the data.

I am considering using a VIEW but am wondering if a VIEW would provide better performance from the point of view that a logical builds a permanent index filtering the records required.

I have run PRTSQLINF and the programs are using existing logicals and is not making any suggestions.

My question is, does a VIEW create a similar retrieval in that it will only read the records in the filter or does it do the filtering at the time the SELECT is executed hence possibly reading all 750 million records therefor not gaining anything?

TIA
Darryl Freinkel
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