Re: CHAIN Versus SETLL and READ When Data Needed

Shannon - in my opinion (for what its worth --- and that quote is directly
form my wife) the answer unfortunately is ---
It depends
Will you get a lot more NOT founds than you will get more founds?
If the answer is YES, then the SETLL is the way to go
otherwise - if you get lot more founds than not founds, then the CHAIN is
the way to go.
Where the break point is, I'm not too sure, and I'm not too sure how you
would try and find out.



Alan Shore

NBTY, Inc
(631) 244-2000 ext. 5019
AShore@xxxxxxxx


rpg400-l-bounces@xxxxxxxxxxxx wrote on 02/28/2007 02:27:25 PM:

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.











--
This is the RPG programming on the AS400 / iSeries (RPG400-L) mailing

list

To post a message email: RPG400-L@xxxxxxxxxxxx
To subscribe, unsubscribe, or change list options,
visit: http://lists.midrange.com/mailman/listinfo/rpg400-l
or email: RPG400-L-request@xxxxxxxxxxxx
Before posting, please take a moment to review the archives
at http://archive.midrange.com/rpg400-l.