RE: CHAIN Versus SETLL and READ When Data Needed

If this logic exists within a loop our current standard is the setll and
then the reade.  A construct in many of our programs is:

Setll (key1) file;
Reade (key1) file;
Dow not %EOF(file);
   process stuff
   Reade (key1) file;
Enddo;

A chain sets %found and reade sets %eof so it makes the test on the dow
easier.  We used to do it the other way when we were using indicators
but we found this more efficient when they were removed.

Scott Feddersen
The Buckle, Inc.



-----Original Message-----
From: rpg400-l-bounces@xxxxxxxxxxxx
[mailto:rpg400-l-bounces@xxxxxxxxxxxx] On Behalf Of Lim Hock-Chai
Sent: Wednesday, February 28, 2007 1:34 PM
To: RPG programming on the AS400 / iSeries
Subject: RE: CHAIN Versus SETLL and READ When Data Needed


My vote would be using chain:
Reasons:
1) Make code more readable.
2) I think chain is faster.  When chaining record not found, it would be
like setll, no data to load.  If chain is found it go ahead and load the
data.  Using setll and read require one extra step.
 



-----Original Message-----
From: rpg400-l-bounces@xxxxxxxxxxxx
[mailto:rpg400-l-bounces@xxxxxxxxxxxx] On Behalf Of Shannon O'Donnell
Sent: Wednesday, February 28, 2007 1:27 PM
To: RPG programming on the AS400 / iSeries
Subject: CHAIN Versus SETLL and READ When Data Needed

I posed this question on MCPressOnline the other day but I would like to
get more opinions on it so I'll post it here too.   A shop-standard
hangs in the balance.

 

   Assume that you have an RPG program that has logic such that you need
to first see if some data is in a file, based on a key, and then if so,
you do something with that data.

 

   Further assume that this file has a complex key with three fields.   

 

    The program logic is such that you check the maximum number of keys
for a match down to the minimum number of keys

 

     Like this:

 

              Key1    Klist

                          Kfld              Fld1

                          Kfld              Fld2

                          Kfld              Fld3

 

              Key2     Klist

                          Kfld              Fld1

                          Kfld              Fld2

 

              Key3     Klist

                           Kfld             Fld1

 

 

   Which one of these logic blocks is most efficient?

 

   Key1   Setll   file

       If    %FOUND(file)

               Key1   READE file

                       Use Fields

       Else

          Key2    Setll  File

            If   %FOUND(file)

                     Key2 Use Fields

           Else

             Key3  Setll File

                  If   %FOUND(file)

                     Key3 READE file

               Endif

            Endif

          Endif

                  

 

 

OR....

 

               KEY1  Chain file

                          If       %FOUND(file)

                              Use fields

                         Else

              KEY2   Chain  file

                          If      %FOUND(file)

                              Use Fields

                          Else

              KEY3   Chain file

                          If   %FOUND(file)

                             Use Fields

                         Endif

                         Endif

                         Endif

 

 

My opinion is that the CHAIN is more efficient from both a
coding/maintenance standpoint and from an I/O standpoint, but I'm open
to opinions.

 

 

 

 

 

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