RE: Record size limitation in RPG - MQ Series/User Spaces

Hi Carl,

>  D p_UsrSpc        S               *
>  D dsLH            DS                   BASED(p_UsrSpc)
>  D   dsLHFill1                  103A
>  D   dsLHStatus                   1A
>  D   dsLHFill2                   12A
>  D   dsLHHdrOff                  10I 0
>  D   dsLHHdrSiz                  10I 0
>  D   dsLHLstOff                  10I 0
>  D   dsLHLstSiz                  10I 0
>  D   dsLHEntCnt                  10I 0
>  D   dsLHEntSiz                  10I 0
>
> For some strange reason, dsLHFill1 contains the 1st 103 characters of my
> data.  I am passing the value of dsLHLstOff as the pointer to my buffer
> data.  This program is using a 3.7 ILE compiler.  I know I am close, but
> unsure what to do next.  I thought the value of dsLHLstSiz would contain the
> length of my user space, but it does not.

That code looks familiar! :)  (I wrote that code 6 years ago.. you must've
found it in the archives)

That data structure is returned by many of IBM's APIs... the APIs that
they call "List APIs" return data in that format.

However, in your case, you're populating the user space yourself rather
than asking IBM's list APIs to populate it.  So, it won't be in that
format (unless you specifically write it that way.)

A user space is merely a big flat space.  If you have a user space that's
4mb in size, it's like having a file with a single record that's 4mb long,
and with no external definition.   You can put absolutely any data that
you want into the user space -- there's no predefined format whatsoever.

In this case, you've got a pointer to the start of your user space.  Any
variable that's based on that pointer will occupy the same memory as the
start of your user space.  You can store any data you like in that area,
and when you view that variable it'll be populated with the underlying
bytes that are in the user space.

And that's what you've done here... you've loaded your message into the
user space, and then used that dsLH data structure to view that data.
What you'll see in that structure is the bytes that happen to be in that
part of the space.

Does that make sense?