RE: Using CHAIN instead of SETLL AND READE to begin a loop which reads a group

[Jim Langston <jlangston@xxxxxxxxxxx>]

In my experience it has been FIFO, but you have to realize what
"unpredictable" means, same thing as "undefined".  It means that in V5R2 it
may be the last record if it makes the compiler easier to make.  Means
whatever it returns now doesn't' necessarily mean it will return the same
thing tomorrow, so don't count on it.

Regards,

Jim Langston

-----Original Message-----
From: Frank.Kolmann@revlon.com [mailto:Frank.Kolmann@revlon.com]
Sent: Sunday, May 12, 2002 8:55 PM
To: rpg400-l@midrange.com
Subject: Using CHAIN instead of SETLL AND READE to begin a loop which
reads a group


Looks to me like the issue here is
'What does CHAIN retreive when used on a file with duplicate keys.'
Long time ago I was told by IBM that the record retreived by the
CHAIN is unpredictable.
Experience tells that the retreival is FIFO.
Has anyone noticed anything other than the above.

Frank Kolmann


>To: rpg400-l@midrange.com
>From: "Mark Adkins" <adkinsm@amerch.com>
>
>I can't find any documentation that addresses this.
>
>If there is a table of order detail which has an index on Order #, and
UPC.
>Will these two pieces of code execute identically.
>
>1.   MYORD#    CHAIN     ORDDTL    99
>     *IN99          DOWEQ*OFF
>               <SOMECODE>
>     MYORD#    READE     ORDDTL          99
>               ENDDO
>
>2.   MYORD#    SETLL     ORDDTL
>     MYORD#    READE     ORDDTL          99
>     *IN99          DOWEQ*OFF
>               <SOMECODE>
>     MYORD#    READE     ORDDTL          99
>               ENDDO
>
>What if the index is not unique?  What if I set my pointer past the end of
>file before execution?
>
>Human logic dictates that a CHAIN should return the first occurrence of
the
>index which would be the smallest upc.  Computer implementation dictates
>that the CHAIN should return the first occurrence of MYORD# found via an
>algorithm.
>
>Mark


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