PROCEDURE "ProcEMUpdPrimary" (IN "ParResCode" INTEGER)
EXTERNAL NAME "RCServer_EM"

the call:

CALL ProcEMUpdPrimary(-1);

and this is the access:

ResCode := Params.FindParam('ParResCode').AsInteger;

If I change the JOB to pass a variable instead, everything works fine:

DECLARE ResCode INT DEFAULT -1;
...
CALL ProcEMUpdPrimary(ResCode);