Debug Procedures for a Wait EI CP Disabled Wait
Use ALTER/DISPLAY console mode (if available), to display real PSW. Also, display general and extended control registers and storage locations X'OO'- X'1 0'. Force a SYSTEM RESTART to cause a CP ABEND dump to be taken. IPL. CP Enabled Wait
Force a SYSTEM RESTART 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
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 or CP VMDUMP command (or CMS DUMP subcommand)
to take a dump. Virtual Machine Enabled Wait
Take a dump using the CP DUMP or CP VMDUMP command.
Debug Procedures for a Loop CP Loop
Use ALTER/DISPLAY console mode (if available) to display real PSW. general registers, control registers, and storage locations X'OO- X'10' II Force a SYSTEM RESTART to cause a CP ABEND dump to be tab". II Examine the CP internal trace table to see where the loop is. II II II Virtual Machine Disabled Loop
Use the CP TRACE or CP PER command to trace the loop. Display the general registers and control registers via the CP DISPLAY command.
Take a dump using the CP DUMP or CP VMDUMP command.
Examine the source code. Virtual Machine Enabled Loop Trace the loop, using CP TRACE or CP PER. Figure 63. Debug Procedures for Waits and Loops II Display the PSW, general registers, and extended control registers. II Take a dump, using CP DUMP or CP VMDUMP command. II Examine the source code.
Introduction to Debugging 473

Debug Procedures for Unexpected Results
Unexpected Results in CP Check that the program is not violating and CP restrictions. Check that the program and operating system running 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 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 CP ABEND 1I II Find out why CP abnormally terminated. Examin the PROPSW, I NTPR, SVCOPSW, and CPABEN D 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. CMS ABEND
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
LASTEXEC and PREVEXEC and DEVICE Look at the last instruction executed. Take dump if need be.
Virtual Machine ABEND(other than CMS) Examine dump, if there is one.
Use CP commands to examine registers and control words.
Use CP TRACE or CP PER to trace the processing up to the point where
the error occurred.
Figure 64. Debug Procedures for Unexpected Results and an Abend
474 VM/SP System Programmer's Guide