Re: SQL question

[Vernon Hamberg <hambergv@xxxxxxxxxxxxxx>]

Ravi

At 01:28 PM 6/18/1998 -0500, you wrote:
>Rick,
>
>That is a good point. I did not try that. Maybe it retrieves a page
>worth of records at a time and tht's why the first query was faster.

Usually, the query engine retrives 2 screens of records. This is like
*FIRSTIO on OPNQRYF. So, you can roll down one page before more records
need to be retrieved. After this, records are retrieved in full blocks, 32k
in size, I think.

You can affect the optimization process by using the 'OPTIMIZE FOR nnn
ROWS' clause at the end of your SQL statement. I think 'OPTIMIZE FOR 1 ROW'
is like *FIRSTIO, 'OPTIMIZE FOR 9999 ROWS' is like *ALLIO.

You can get suggestions for improving performance of SQL by running

        CHGQRYA QRYTIMLMT(0)

and

        STRDBG

When the message about exceeding the time limit appears, take the 'C'
option. Then look at you job log. There'll be lots of messages about what
the optimizer did and what would work better.

HTH

Vernon Hamberg
Systems Software Programmer
Old Republic National Title Insurance Company
400 Second Avenue South
Minneapolis, MN  55401-2499
(612) 371-1111 x480


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