EDGTVEXT issues messages when errors are encountered. EDGTVEXT sets the parameter list return code value to zero. EDGTVEXT does not always pass a zero return code in register 15 back to the caller. EDGTVEXT issues a non-zero return code in the register 15 return code from subsystem requests attempted by EDGTVEXT. You can obtain information about the return codes in z/OS MVS Using the Subsystem Interface.