(Re)set POSTPROC field of a datafile
A = SETPOSTPROC(A,MAPPING)
Sets the mappings stored in A.POSTPROC. The size of the datafile A is set to the output size of PRMAPPING. A call without MAPPING clears A.POSTPROC. The size of the datafile A is reset to undefined (0).
The mappings in A.POSTPROC may be extended by ADDPOSTPROC.
Mappings in A.POSTPROC are stored only and executed just after A is converted from a DATAFILE into a PRDATASET.