JCL GO B JCL GO BTransfers control to the statement following the most recent M (mark) command executed.
G B
GO B
GOTO B
GO B goes back to the last executed M, no matter where it is located in the program.
If a "mark" has not previously been executed, the program will terminate with an error message:
Can't find mark at line n in programname
001 PQN
.
010 MV #1 "SSELECT SALES BY MONTH"
011 STON
012 MV #1 "PQ-SELECT 1"
013 P
014 M
015 MV %1 !1
016 IF # %1 GO F
017 C Process the record
.
025 GO B
026 M
Lines 10 to 13 create a sorted list of the records in the SALES file. After each record is processed, the GO B command on line 25 returns control to the M command on line 14. When the end of the list is reached, the IF command on line 16 transfers control to the M command on line 26.
001 PQN
.
009 MV %1 ","
010 M
011 IF # %1 GO 30
012 M
013 IF # %2 GO 40
014 GO 50
015 30 MV %1 "ABC"
016 GO B
017 40 MV %2 "DEF"
018 GO B
019 50 ....
This example simply serves to demonstrate how the GO B command will remember the last M command rather than search backwards for it. First, the values in %1 and %2 are set to null in line 9 and the M at line 10 is recorded. When control reaches line 11, %1 is tested and control is transferred to label 30 on line 15. The intervening M command (at line 12) is not recorded. Line 15 assigns a value of ABC to %1 and line 16 transfers control back to the M on line 10. %1 does have a value now, so control moves on to line 12 and the M on this line is recorded. Next, %2 is tested at line 13 and control is transferred to label 40 on line 17. When the GO B is processed on line 18, control is transferred back to line 12.
JCL