Re: CHAIN versus SETLL

[rbbaird@xxxxxxxxxxx (Rick Baird)]

PaulMmn wrote:

> >>  C    KEY    CHAINFILE            90
> >>   *
> >>  C    *IN90  IFEQ *ON
> >>  .......etc.
> >>
> >>  this makes it pretty obvious that the programmer has a complete key, and
> >>  wants to know if "a particular" record exists or not.
> 
> Not necessarily, Kimosabee!  The AS/400 allows you to chain with a -partial-
> key and match on the part you provide!  (I forget if this only works with a
> composite key (ie more than 1 field) and if you have to use complete fields
> as the partial key)

True.  In that case, (without a subsequent read) you could/would be
validating only the first field(s).  And as another post said, if you
were only validating the fields without the need for the value of the
record you accessed, it could/would be more efficient to use the setll.

As far as read-ability is concerned, I think that many programers aren't
aware (or just don't care) of this aspect of the setll opcode, but in
this case, it wouldn't hurt them to crack a manual, just this once  :)

Rick
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