Procedure for pre-MVS/SP Version 4 libraries

Use this determination method when the source code is compiled against pre-MVS/SP Version 4 macro libraries. (Note: The UCB macros must be included in the macro library concatenation.)

            L    10,X'10'               Load CVT pointer
            USING CVT,10
            TM   CVTDCB,X'08'           Is the OSLEVEL extension present?
            BNO  INVOKE_LIM             No, pre-MVS/SP Version 3 system
            TM   X'4F0'(10),X'08'       General methods supported?
            BNO  INVOKE_LIM             No, general methods unavailable
            UCBLOOK ........            Invoke general method
            B    BYPASS_LIM             Branch around limited method
INVOKE_LIM  DS 0H
            IOSLOOK                     Invoke limited method
BYPASS_LIM  DS 0H