I beg to differ, or rather the manuals themselves do...
Yes You can look at the manuals for the IGGCSI00 interface
and You will see that IGGCSI00 is called from assembler with a standard parameter list
and can be called from REXX using the proper form
also for the TS...
see for rexx
sys1_samplib(iggcsirx)
/********************************************************************/ 03100000
/* */ 03150000
/* ISSUE LINK TO CATALOG GENERIC FILTER INTERFACE */ 03200000
/* */ 03250000
/********************************************************************/ 03300000
ADDRESS LINKPGM 'IGGCSI00 MODRSNRC CSIFIELD DWORK' 03350000
the same called from assembler
sys1_samplib(iggcsilc)
LA 1,PARMLIST 02750000
CALL IGGCSI00 02800000
LTR 15,15 TEST RETURN CODE 02850000
.....
PARMLIST DS 0D 15600000
DC A(MODRSNRT) MODULE/REASON/RETURN 15650000
DC A(CSIFIELD) 15700000
DC A(DATAAREA) 15750000