April 1, 1981
Debug Procedures for a Wait
CP Disabled Wait Use AL TER/DISPLAY console mode (if available), to display real PSW and CSW. Also, display general and extended control registers and storage locations X·OO·-X·l00·. Press SYSTEM RESTART button to cause a CP ABEND
dump to be taken. IPL. CP Enabled Wait --------------------------------4 Press SYSTEM RESTART button to cause a
CP ABEND dump to be taken.
Use the dump to check the status of each VMBLOK. Also, check RCHBLOK. RCUBLOK. and RDEVBLOK for each device. Virtual Machine Disabled Wait --------------------------1 Use CP commands (CMS users may use the CMS DEBUG command) to display
the PSW, CSW, general registers, and control registers.
Use the CP DUMP command (or CMS DUMP subcommand) to
take a dump. Virtual Machine Enabled Wait --------------------------/
Take adump.
Debug Procedures for a Loop Use ALTER/DISPLAY console mode (if available) tei
display real PSW, general registers. control registers, and storage locations X·OO·-X·l00·. Press SYSTEM RESTART button to cause a CP
ABEND dump to be taken.
Examine the CP internal trace table to see where the loop is. Virtual Machine Disabled Loop --------------------------1 Use the CP TRACE command to trace the loop.
Display the general registers and control llegisters via the CP DrSPLA Y command.
Take a dump using the CP DUMP command.
Examine the source code. Virtual Machine Enabled Loop --------------------------1
Trace the loop. Display the PSW, general registers,
and extended control registers. Take a dump. Examine source code.
Debug Procedures for Waits and Loops
16 IBM VM/J70 System programmer's Guide
Figure 5.
Debug Procedures for Unexpected Results Unexpected Results in CP --------------------------.., II II Check that the program is not violating any CP restrictions. Chec* that the f}fogram and {}j)efating system ftmfling on the virtual machine are exactly the same as those
that ran on the real machine.
Use the CP TRACE command to trace CCWs, SIOs, and interrupts.
Look for an error in CCW translation or interrupt reflection . If disk I/O error, use the CP DDR (DASD Dump Restore)
program to print the contents of any disk.
Unexpected results in a virtual machine ----------------------1 l! Check that the program executing on the virtual machine is exactly the same as the one that ran on the real machine.
Make sure that operating system restrictions
are not violated. Use CP TRACE to trace all I/O operations.
Debug Procedures for an ABEND II II Find out why CP abnormally terminated. Examine the PROPSW, INTPR, SVCOPSW, and CPABEND fields in the PSA from the dump. Identify the module that caused the ABEND.
Examine the SAVEAREA, BALRSAVE, and FREESAVE areas of the dump. If I/O operation, examine the real and virtual I/O control blocks. II Determine reason for ABEND from code in ABEND
message DMSABN148T.
Enter debug environment or CP console function mode
to use the commands, to display the PSW, and to examine low storage areas: LASTLMOD and LASTTMOD LASTCMND and PREVCMND LAST EXEC and PREVEXEC and DEVICE Look at the last instruction executed.
Take dump if need be.
Virtual Machine ABEND (other than CMS) ---------------------; II II Examine dump. if there is one.
Use CP commands to examine registers and
control words. Use CP TR,a,CE the '.....j.:; the point where the error occurred.
Debug Procedures for Unexpected Results and an Abend
Part 1. Debugging with Vft/370 17
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