RE: writing to userspace

A simpler way to do it is to let the compiler handle the pointer math for you. 
This works find as long as you will not have more than 65537 records for array 
of records or 32767 for multiple occurrence data structure. 

First way is to use a multiple occurrence data structure.  

d dsStructure...
d                           ds                      Qualified
d                                                   Occurs(32767)
d                                                   Based(ptrStructure)
d  YourField1...
d  Yourfield2...
 /free

  ptrStructure = USPC_GetPointerToUserSpace(...);

  // From this point on, just treat like any multiple occurrence data 
structure. 
  // When you occurs, system does pointer math. 
 For x = 1 to Top;
  %Occurs(dsStructure) = x;
   dsStructure.YourField1 = (Your Code);
   dsStructure.YourField2 = (Your code);
EndFor;
  
Other way is to use array of records. 

d myArray...
d                        ds                          Qualified
d                                                    Dim(65534)
d                                                    Based(ptrArray)
d   YourField1...
d   YourField2...
 /Free

  ptrArray = USPC_GetPointerToUserSpace(...);

  // Now you can just treat as array and compiler does pointer math. 

  For x =- 1 to Top;
    myArray(x).YourField1 = (Your code);
    myArray(x).YourField2 = (Your code);
  EndFor;

Either way is best. Easy to screw up pointer math. 

got a userspace (which is set to autoextend) and in my rpg program i am
retrieving a pointer to that userspace. through pointer arithmetic i am
filling the userspace with some values.

D usPtr           S               *
D usData          DS                  based(usPtr) qualified
D   header                            likeds(wws_main_us)

D usDataPtr       S               *
D vkst            S              5  0 based(usDataPtr)

dow (not %eof);
  usDataPtr = usPtr + %len(usData.header) +

 >>             (i * %size(vkst));
 >> vkst = someValue;
 >>  i += 1;
 >> read file;

enddo;