If you specify UNAUTH=NO or omit UNAUTH, the service can abend if an error occurs or if your program is holding a lock. The return, reason, and abend codes for UNAUTH=NO are as follows:
When control returns after invoking SWAREQ, check the return code in GPR 15. If the return code is 0, the service is successful. Otherwise, the service failed, and the non-zero return code in GPR 15 is also the reason code associated with the failure. There is only one reason code: reason code hexadecimal 38, which means that the system could not obtain the storage necessary to carry out the request.
When control does not return from SWAREQ, an abend occurred. To interpret the abend dump, use the contents of GPRs 1 and 15. GPR 0 contains the address of an area that contains diagnostic information. This area is further described in z/OS MVS Programming: Authorized Assembler Services Reference SET-WTO. GPR 1 contains abend code 0B0. GPR 15 has the reason code associated with the abend.