IDENTIFYING THE PROBLEM Two types of problems are eas1lY identified: abnormal termination is
indicated by an error message, and unexpected results become apparent onoe the output is examined. The looping and wait state conditions are not as easily identified. When using VM/370, you are nor.ally sitting at a terminal and do not
have the lights of the processor control panel to help you. You may have
a looping condition if your program takes longer to execute than you
anticipated. Also, check your output. If the number of output records or
print lines is greater than expected, the output may really be the same
information repeated many times. Repetitive output usually indicates a
program loop_ Another way to identify a loop is to periodically examine the current If the PSW instruction address always has the same value, or if the
instruction address has a series of repeating values, the program
probably is looping. The wait state is also difficult to recognize when at the terminal.
Again, the console lights are If your program is taking
longer than expected to execute, the virtual machine may be in a wait state. Display the current PSW on the terminal. Periodically, issue the CP command QUERY TIME and compare the elapsed processing time. When the elapsed processing
time does not increase, the wait state probably exists.
Figure 2 helps you to identify problem types and the areas where they may occur. Part 1. Debugging with VM/370 7

r,-----------------------------------------------------------------------, tProblemt Where t I Type tAbend Occurst Distinguishing Characteristics
Abend CP abend CP abend
The alarm rings and the message DMKDMP9081 SYSTEM FAILURE, CODE XXX XXX appears on the processor console. In this
instance, the system dump device is a disk, so
the system dumps to disk and automatically
restarts. If an error occurs in the dump,
checkpoint, or warmstart program, CP enters the
wait state after issuing ene or more of the
following messages: DMKDMP905W SYSTEM DUMP FAILURE; PROGRAM CHECK DMKDMP906W SYSTEM DUMP FAILURE; MACHINE CHECK, RUN SEREP DMKDMP907W SYSTEM DUMP FAILURE; FATAL I/O ERROR DMKCKP900W SYSTEM RECOVERY FAILURE; PROGRAM CHECK DMKCKP901W SYSTEM RECOVERY FAILURE; MACHINE
CHECK, RUN SEREP DMKCKP902W SYSTEM RECOVERY FAILURE; FATAL I/O ERROR DMKCKP922W SYSTEM RECOVERY FAILURE; INVALID SPOOLING DATA DMKCKP910W SYSTEM RECOVERY FAILURE; INVALID WARM START CYLINDER DMKCKP911W SYSTEM RECOVERY FAILURE; WARM START AREA FULL DMKCKS903W SYSTEM RECOVERY FAILURE; VOLID xxxxxx ALLOCATION ERROR CYLINDER xxx n DMKCKS912W SYSTEM RECOVERY FAILURE; VOLID xxxxxx NOT MOUNTED DMKCKS915E PERMANENT I/O ERROR ON CHECKPOINT CYLINDER DMKCKS917E CHECKPOINT CYLINDER INVALID; CLEAR STORAGE AND CCLD START DMKWRM921W SYSTEM RECOVERY FAILURE; UNRECOVER­ ABLE I/O ERROR DMKWRM903W SYSTEM RECOVERY FAILURE; VOLID xxxxxx ALLOCATION ERROR CYLINDER xxx DMKWRM904W SYSTEM RECOVERY FAILURE; INVALID WARM START DATA DMKWRM912W SYSTEM RECOVERY FAILURE; VOLID xxxxxx NOT MOUNTED tThe following messages appear on the processor
t console: I I DMKDMP9081 SYSTEM FAILURE, CODE xxx xxx I DMKDMP9601 SYSTEM WARM START DATA SAVED I DMKDMP961W SYSTEM SHUTDOWN COMPLETE Figure VM/370 Problem Types (Part 1 of 6)
8 IBM 1M/370 System Programmerfs Guide