Re: MQSeries Question

Hi Alistair,

>
> We have recently been exploring the MQ route and I have a question f
>  the MQ API boffins out there.  We may well be receiving messages
>  om excess pf 32K.  Since the MQGET API specifies that you must
>  retrieve the message into a single RPG-ILE variable, you are
>  limited to 32K as a maximum message length.
>
> My question is, therefore, how would you retrieve a message longer
>  than 32K.

First of all, let me state that I'm not at all familiar with MQSeries,
but I've had to deal with similar situations in which an API returns
a string thats too big for RPG to deal with directly.

I'm assuming that the API that you're calling passes a string by
reference.  (all dynamic calls do this, and bound calls do if the
keyword "value" is not specified)

Okay, finally to my solution...   When you pass a parm by reference,
it only actually passes the address of the parameter to the other
program.   If you were to pass a shorter variables that's based in
the same area as a user-space, you could (effectively) pass a
string thats up to 16MB long... :)

Here's a quick (untested) example:

D CrtUsrSpc       PR                  ExtPgm('QUSCRTUS')
D   peUsrSpc                    20A   CONST
D   peExtAtr                    10A   CONST
D   peInitSiz                   10I 0 CONST
D   peInitVal                    1A   CONST
D   pePubAuth                   10A   CONST
D   peText                      50A   CONST
D   peReplace                   10A   CONST
D   peErrors                   256A

D RtvPtrUS        PR                  ExtPgm('QUSPTRUS')
D   peUsrSpc                    20A   CONST
D   pePointer                     *


D dsEC            DS
D*                                    Bytes Provided (size of struct)
D  dsECBytesP             1      4B 0
D*                                    Bytes Available (returned by API
D  dsECBytesA             5      8B 0
D*                                    Msg ID of Error Msg Returned
D  dsECMsgID              9     15
D*                                    Reserved
D  dsECReserv            16     16
D*                                    Msg Data of Error Msg Returned
D  dsECMsgDta            17    256

D p_Var           S               *
D Var             S              1A   BASED(p_Var)
D VarMaxLen       S             10I 0

c                   eval      dsECBytesP = 256

C                   callp     CrtUsrSpc('SPACE     QTEMP':'USRSPC':
C                             1:x'00':'*ALL':'Big string from API':
c                             '*YES': dsEC)

c                   if        dsECBytesA > 0
c***  handle failure to create user space here
C                   endif

C                   callp     RtvPtrUS('SPACE     QTEMP':p_Var)

C* 16MB
c                   eval      VarMaxLen = (16*1024*1024)

c                   call      'MYAPI'
c                   parm                    Var
c                   parm                    VarMaxLen

c                   eval      *INLR = *On

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