Re: mi access to a dtaara

["Simon Coulter" <shc@xxxxxxxxxxxxxxxxx>]

Œ
Hello Steve,

You wrote:
>it is kind of odd that qxxchgda is not documented in the api reference.  But
>since there are C pgms that call it, I assume that access to it cannot be
>revoked in the future.

This is no longer an MI question but I'll answer it here.  Further discussion 
on these specific questions should be directed to the MIDRANGE-L, RPG400-L, or 
C400-L lists.

The C interface is unlikely to be revoked although the QWCRDTAA API is a better 
choice for retrieving the contents of a data area than QXXRTVDA.  What may 
happen is that IBM might alter the #pragma definition such that function calls 
to QXXCHGDA actually invoke a completely different program.  Since the QXXCHGDA 
program itself has never been a documented API they can do this although that 
would require a recompile to pick up the new linkage so I doubt it would 
actually happen.

>note the following in the doc of qxxchgda:
>    "QXXCHGDA can only be used to change character data. "

That is a limitation of the specific program.  QXXRTVDA allows retrieval of 
character data areas only so at least they are consistent.

Save yourself some effort.  QXXRTVDA and QXXCHGDA only support character data 
areas but they do support DDM character data areas.

Because they invoke the underlying command processing programs which do normal 
parameter validation they are restircted to character data areas.  QXXRTVDA 
calls QCLRTVDA which is the CPP for RTVDTAARA.  QXXCHGDA calls QWCCCHVC which 
is the CPP for CHGDTAARA.

One of the rules imposed by the CPPs is that you cannot substring a decimal or 
logical data area.  The QXX???DA programs always build the call to the CPP 
using substring information (i.e., position and length). It wouldn't have taken 
much effort to build the call like the command analyzer does, using special 
values (e.g., -1) to indicate no substring and then these programs would work 
with all data areas.  I suspect these functions were added at the request of a 
customer, business partner, or other IBM unit, and therefore do only the 
minimum required function.

>I am going to find out myself, but if anyone knows, does the rpg in and out
>have the same restriction? does rpg ile also use IN and OUT?

RPG IV allows all the data area types to be used directly.  IN and OUT are 
still the method for handling data areas unless you want RPG to automatically 
read the data area at program initialisation and update it at program 
termination (however, data areas are a quick and dirty solution and should be 
avoided).

>also, does the rpg IN and OUT handle a *ddm data area?

Yes.

>how does a C pgm chg a *ddm or logical data area?  does it have to call a cl
>pgm that runs ChgDtaAra?

Well it could call an RPG IV program ..... :)

If you just need a 'data area' rather than a *DTAARA then use a space instead.

Regards,
Simon Coulter.

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