Type ASSEMBLE
Source Lines : 1,300
Fixes Applied : 8
Most Recent Version : Thursday, December 7, 1978
Last Fix ID : [R15003DK]

Function

          WHILE EXECUTING A CP GENERATED TAPE CHANNEL PROGRAM.
          POSITIONING OF THE TAPE WILL BE REQUIRED ON READ/WRITE
          COMMANDS AND THE CHANNEL PROGRAM RE-EXECUTED.
          IF THE ERROR CONDITION IS UNCORRECTABLE A CALL WILL BE
          ISSUED TO THE MESSAGE WRITER (DMKMSW) FOR OPERATOR
          AWARENESS. ON REGAINING CONTROL FROM DMKMSW THE ORIGINAL
          CHANNEL PROGRAM MAY BE RE-EXECUTED OR TERMINATED.

           TO ISSUE A RELEASE CCW TO TAPE DEVICE TO DETERMINE
           IF HARDWARE HAS 2/4 CHANNEL SWITCH.

Operation

               ADDRESS OF THE IOERBLOK IN THE RDEVBLOK.
            B. TEST FOR CHANNEL ERROR.
               1. INTERFACE AND CHANNEL CONTROL CHECKS ARE RETURNED
                  TO THE CALLER WITH IOBSTAT=IOBFATAL.
            C. TEST FOR OTHER TYPE ERROR.
               DESIGNATION OF COMMAND BEING EXECUTED
                      C=CONTROL
                      R=READ
                      W=WRITE
               1. EQUIPMENT CHECK (C,R,W) PERFORM ACTION 10.
               2. BUS-OUT CHECK (C,R,W)   PERFORM ACTION 4.
               3. INTERVENTION REQUIRED (C,R,W) PERFORM ACTION 3.
               4. COMMAND REJECT (C,R,W) PERFORM ACTION 13.
               5. OVERRUN (R,W) PERFORM ACTION 7.
               6. LOAD POINT (C,R) PERFORM ACTION 12.
               7. DATA CHECK (R) PERFORM ACTION 5.
               8. DATA CHECK (W) PERFORM ACTION 6.
               9. DATA CHECK (C) PERFORM ACTION 8.
              10. CHANNEL DATA CHECK (R,W) PERFORM ACTION 7.
              11. CHANNEL DATA CHECK WITH DATA CONV ON (R) PERFORM
                  ACTION 13.
              12. CHANNEL DATA CHECK AND NOT CAPABLE ON (R) PERFORM
                  ACTION 9.
              13. CHANNEL DATA CHECK AND NO PREVIOUS SENSE BITS ON
                  (R,W,C) PERFORM ACTION 10.
              14. CHAINING CHECK (R) PERFORM ACTION 7.
              15. PROGRAM CHECK (R,W) PERFORM ACTION 12.
              16. PROTECTION CHECK (R,W) PERFORM ACTION 12.
              17. INCORRECT LENGTH (R,W) PERFORM ACTION 12.

                ****************
                * ACTION  LIST *
                ****************

              3. CHECK TO SEE IF TAPE DRIVE IS EXISTENT. IF
                 NON-EXISTENT ISSUE OPERATOR MESSAGE.
                 IF THE COMMAND WAS A REWIND-UNLOAD EXIT. OTHERWISE
                 SET INTERVENTION REQUIRED FLAGS AND WAIT FOR THE
                 DEVICE END INTERRUPT. WHEN THE DEVICE END
                 INTERRUPT OCCURS RE-ISSUE THE ORGINAL CCW STRING.
              4. RE-ISSUE THE COMMAND IF 'DEVICE END' STATUS IS
                 NOT PRESENT. IF 'DEVICE END' IS PRESENT DURING A
                 WRITE, REPOSITION THE TAPE AND RE-ISSUE THE
                 COMMAND. ALLOW A MAXIMUM OF 5 RETRIES.
              5. RETRY ORIGINAL CCW STRING 40 TIMES WITH TAPE
                 CLEANING ACTION PERFORMED EVERY 4'TH TIME. IF THE
                 ERROR STILL PERSISTS READ OPPOSITE RECOVERY WILL
                 BE ATTEMPTED.
              6. REPOSITION TAPE AND ISSUE AN ERASE COMMAND, THEN
                 FOLLOW WITH THE ORIGINAL CCW STRING FOR A MAXIMUM
                 OF 15 RETRIES.
              7. REPOSITION TAPE AND RE-ISSUE COMMAND FOR A MAXIMUM
                 OF 5 RETRIES.
              8. IF COMMAND IS A 'WTM', EXECUTE ACTION 6. IF THE
                 COMMAND IS AN 'ERASE GAP' RETRY THE COMMAND FOR 3
                 RETRIES.
              9. REPOSITION TAPE TO LOAD POINT AND ISSUE OPERATOR
                 MESSAGE.
             10. CALL DMKMSW.
             12. SET IOBSTAT=IOBFATAL AND RETURN TO CALLER.
             13. CALL DMKMSW.



            D. IF THE RETRY PROCEDURE HAS BEEN EXHAUSTED AND
               UNSUCCESSFUL CALL DMKMSW FOR OPERATOR OPTIONS.
               (CANCEL,RETRY,IGNORE)
               THE RESPONSES ALLOWED WILL BE BASED ON THE CONDITION
               CAUSING THIS ERROR.

Calls to Other Routines

         DMKTAPER -
                    1. DMKMSW - TO PROVIDE OPERATOR COMMUNICATION
                                IN ATTEMPTING TO CORRECT THE ERROR
                                CONDITION.
                     2. DMKIOEST - TO UPDATE STATISTICAL COUNTERS

         DMKTAPRL -
                     1. DMKIOSQR - PERFORM TIO/REL
                     2. DMKPTRUL - UNLOCK DMKTAP PAGE

         DMKTAPER/DMKTAPRL
                     1. DMKFREE - TO OBTAIN STORAGE FOR WORK AREAS
                     2. DMKFRET - TO RETURN STORAGE WORK AREAS.
                    4. DMKIOEST - TO UPDATE STATISTICAL COUNTERS