RE: Sequence error in MR

[Neil Palmer <neilp@xxxxxxxxxxx>]

There's one word missing from this discussion.  Performance. 
Now I'm citing numbers here from 10 years ago at least, on ancient 
hardware, but I rewrote a program someone had written to update a large 
master file from a transaction file.  It was written using either CHAIN or 
SETLL/READ (I can't recall) and I changed it to use MR logic.  The run 
time dropped from approx 4 hours to 40 mins.  And before anyone asks, no I 
don't care to recreate a similar test today, but if anyone want to go 
ahead I'd be happy to hear the results.  :-)

...Neil




G Armour <garmour400m@xxxxxxxxx> 
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2003/09/17 17:01
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RE: Sequence error in MR






Or, even in RPG, how about:

   fBONLPF    IF   E           K DISK
   fBLPART    UF   E           K DISK
   c                   Dou       %eof( BONLPF )
   c                   Read      BONLPF
   c                   If        not %eof( BONLPF )
   c     ORDER         Setll     BLPART
   c                   Dou       %eof( BLPART )
   c     ORDER         Reade     BLPART
   c                   If        not %eof( BLPART )
   c                   Delete    BLPART
   c                   Endif
   c                   Enddo
   c                   Endif
   c                   Enddo
   c                   Eval      *inLR = *On

Try to tell me that most RPG programmers will have to go look at a manual
before they know what's going on in this code.

Also, the original MR example will read every single record in the
secondary file - coupled with the RPG cycle overhead, there is no way the
MR program will perform anywhere close to a properly <g> written program. 
If you've got 1,000,000 records in the secondary file, and end up deleting
5,000 of those records, then 995,000 records are unnecessarily read.

Still, love your SQL example, Rob!

GA

--- rob@xxxxxxxxx wrote:
> Would that be the same as:
> DELETE FROM BLPART 
> WHERE ORD IN(SELECT ORD FROM BONLPF)
<snip> 
> 
> 
> Lurton Keel <LKeel@xxxxxxxxxxxxxx>
> Sent by: midrange-l-bounces@xxxxxxxxxxxx
> 09/17/2003 02:42 PM
> Please respond to Midrange Systems Technical Discussion
> 
>         To:     "'Midrange Systems Technical Discussion'" 
> <midrange-l@xxxxxxxxxxxx>
>         cc: 
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>         Subject:        RE: Sequence error in MR
> 
> 
> Mark,
> We still have 6 or so MR programs that have worked flawlessly for the
> past 20 years.
> Almost all of them are deletion programs that remove shipped, paid etc.
> items from master files.
> Following is an example of one of our programs. 
>      FBONLPF    IPE AE           K DISK
>      FBLPART    US  AE           K DISK
>      IBILL1         01
>      I                                          ORDER           M1
>      IBILL2         03
>      I                                          ORDER           M1
>      OBILLPART  DDEL 03 MR
> 
> MR Rules.