Re: Logical File or OPNQRYF or any other way ? -- MIDRANGE-L

True, and I said that in my earlier reply.

Rob Berendt
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Group Dekko Services, LLC
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6928N 400E
Kendallville, IN 46755
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Al Barsa <barsa@xxxxxxxxxxxxxxxxxxx> 
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Re: Logical File or OPNQRYF or any other way ?







But if you always know the keys for the file, and underlying LF would
certainly help run time performance.

Al

Al Barsa, Jr.
Barsa Consulting Group, LLC

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The imbedded SQL got better in V5R3.

Rob Berendt
--
Group Dekko Services, LLC
Dept 01.073
PO Box 2000
Dock 108
6928N 400E
Kendallville, IN 46755
http://www.dekko.com





Ken Sims <mdrg5003@xxxxxxxxx>
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Hi Malini -

>I have a physical file which has millions of records, and this physical
>file gets updated quite frequently by various programs in the
application.
>
>I have to develop 2 programs pertaining to an enhancement request.
>
>Program 1
>
>Needs to read the file selectively based on two fields of the physical
>file , perform calculations on the selected records and update them.
There
>is no existing logical file on the physical with these 2 fields as a key
>
>Program 2
>
>Needs to read (only)the file selectively. File is opened in input mode
only.
>
>Which is the more efficient method in each case - creating a logical file

>with the 2 fields as key or using an openquery with select on the 2
fields
>before each program is called. Any other efficient way ?

The most efficient way is to have a logical file.

If either of the programs is interactive, or if either program is going to

be run frequently, definitely make a logical file.

If both are going to run in batch and not very often (like a month-end
program), then an OPNQRYF with record selection would probably be
acceptable.

>Also :- What are the scenarios where a logical file is preferred over an
>open query file and vice-versa ?

My response above pretty covers that.  Additionally, even for an
infrequent
batch program, if you need to do keyed operations (rather than just
processing all of the selected records sequentially), the logical file is
better.  In that case the logical file could be MAINT(*REBLD) so that the
access path would be built when the file is opened.

SQL is also an option for batch programs, but personally I find SQL to be
a
real PITA for many reasons, not the least of which is the poor integration

of SQL into the RPG compilers (not the fault of the compiler folks).

--
Ken
http://www.ke9nr.net/
Opinions expressed are my own and do not necessarily represent the views
of
my employer or anyone in their right mind.

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