RE: Another V5R1 query... Qualified DSs

["Stone, Brad V (TC)" <bvstone@xxxxxxxxxxxxxx>]

> -----Original Message-----
> From: Jon.Paris@hal.it [mailto:Jon.Paris@hal.it]
> Sent: Wednesday, May 09, 2001 3:08 PM
> To: RPG400-L@midrange.com
> Subject: Re: Another V5R1 query... Qualified DSs
> 
> 
> 
>  >> What's the difference between:
> 
>  >> 1.  using the QUALIFED keyword on a DS
>  >> 2.  specifying PREFIX('dsname.')?
> 
>  >> Wouldn't they do exactly the same thing?
> 
> No not really.  In the first case the field name does not 
> change - it can
> be identical in multiple DSs.  It is referenced via qualification
> CurrentRec.PhoneNo and PreviousRec.PhoneNo.

But it does.  You can't reference it by just the name.  You have to use the
qualifier.

> 
> In the second case the field name is changed by sticking the prefix in
> front of it e.g. PhoneNo becomes CPhoneNo and PPhoneNo.

But if the prefix is "CurrentRec." then you would reference it as
"CurrentRec.PhoneNo" just as the first case.  Of course, this only applies
to Externally defined DSs and the PREFIX qualifier can't be more than 10 (at
least in V4R4).

> 
> Effectively it comes out to the same thing (effectiely two differently
> named fields) until you consider that with the qualified 
> option you can now
> say that the PreviousRec DS is LIKEDS(CurrentRec) and all the 
> fields and
> their sizes and names come along for the ride!

LIKEDS uses QUALIFIED by default, though.  So again, I don't see a
difference.  In this case, using external DS, definining with the same
EXTNAME keyword is like using LIKEDS.

I guess I'm not trying to argue.  At first I thought this was a great
option.  Then a coworker asked me what the difference between this and
prefixing the DS was.  Now I realize you can only prefix external DSs, so
there is a difference.

But if it's an internal DS, and I use QUALIFIED, that's the same as me
naming each field differently.  And I can still move all the stuff along
with it.

Any specific examples that show it's usefullness?  Anyone?  Bueller?  

Brad
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