Re: OPNQRYF Vs Logical Files

[Vern Hamberg <hambergv@xxxxxxxxxxxxxx>]

At 05:45 PM 8/22/97 -0700, Venu wrote:
>
>
>
>
>Hi All,
>
>     In one of my jobs, I will be processing data from a physical file say
>File1. File1 has 3 members. I will select data from the 2 out of 3 members.
>Also I have a select criteria (select where File1.field1 = xxxx) to process
>the records.
>
>     At present I've created a Logical file over the two members of the PF
>with the Select criteria specified in DDS of the LF. This LF I am using in
>my RPG. But the job processes 1.3 million records from both the members.
>This job runs in batch.
>
>     Our people are suggesting to replace the LF with a OPNQRYF in a driver
>CL. So after discussing the pros and cons, I have 2 alternate ways :

Venu,

I don't think that OPNQRYF is automatically a better solution than LFs.
First of all, every time it runs, it has to go through a query optimization
process that adds overhead to the job and will probably slow it done. In
any case, you need logical files (access paths, or indexes, that is) that
can _support_ the optimization process. And you can't always guarantee that
the optimizer will use the logicals you've set up.

It sounds like you don't need to relate or combine the 2 members, or do you
combine them in the DDS into a single member of the logical file? In either
case, I think the better bet is to keep doing what you are, reading the
logical in key sequence in the RPG, with overrides to separate members (if
any) in the logical file.

A more effective way to speed up the process might be to consider
preloading records in another process, to minimize the physical IO needed
for this program. There's been some discussion of this. Can someone else
provide the details--I'd like to know, too.

Cheers,

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