If you cannot find the cause of the wait or lcop from the information
just gathered, try to reproduce the problem, this time tracing the
processing via the CP TRACE command.
If CMS is running in the virtual machine, the CMS debugging
facilities may also be used to display information, take a dump, or
trace the processing. The CMS SVCTRACE and the CP TRACE commands record
different information. Figure 7 compares the two.
If the virtual machine is in an enabled wait state, try to find out why
no I/O interrupt has occurred to allow processing to resume.
The Control Program treats one case of an enabled wait in a virtual
machine the same as a disabled wait. If the virtual machine does not
have the "real timer" option and loads a PSW enabled only for external
interrupts, CP issues the message DMKDSP450W CP ENTERED; DISABLED WAIT STATE Since the virtual timer is not decreased while the virtual machine is
in a wait state, it cannot cause the external interrupt. A "real timer"
runs in both the problem state and wait state and can cause an external
interrupt which will allow processing to resume. The clock comparator
can also cause an external interrupt.
Three disabled wait conditions can occur during the operation of the RSCS component of VM/370. They can result from either hardware
malfunctions or system generation errors. CP notifies the RSCS operator
of the wait condition by issuing the message DMKDSP450W CP ENTERED; DISABLED WAIT PSW to the RSCS operator's console. Using CP display the virtual machine's PSW. The
characters indicate the error condition.
commands, the operator can
rightmost three hexadecimal !!IT If no RSCS message was issued, a program check
interrupt occurred during the execution of the program check handler. A
programming error is the probable cause.
If the RSCS message DMTREX091T INITIALIZATION FAILURE -- RSCS SHUTDOWN was issued, RSCS operation has been terminated due to an error in the
loading of DMTAXS or DMTLAX. A dump of virtual storage is automatically
taken. Verify that the CMS files DMTAXS TEXT and DMTLAX TEXT are
correctly written and resident on the RSCS system-residence device. 30 IBM System Programmer's Guide

Aug 1, 1979
If the RSCS message DMTREX090T PROGRAM CHECK IN SUPERVISOR -- RSCS SHUTDOWN was issued, the program check handler has terminated RSCS due to a
program check interrupt in other than a dispatched line driver. A dump
of virtual storage is automatically taken. A programming error is the
probable cause.
The wait state code is loaded by DMTREX at RSCS termination or
automatically during program check handling.
If neither of the last two messages was issued, use the CP DUMP command to dump the contents of virtual storage. Do an IPL to restart
the system. If the problem persists, notify the system support
personnel. !AI1 STATE A program check interrupt has occurred during
initial processing, before the program check handler could be activated.
This may be caused by a programming error or by an attempt to load RSCS into an incompatible virtual machine. The latter case can occur if the
virtual machine has (1) an incomplete instruction set, (2) less than
512K of virtual storage, or (3) does not have the required VM/370 DIAGNOSE interface support. The wait state code is loaded automatically
during the initial loading and execution of the RSCS supervisor, DMTINI, DMTREX, DMTAXS, or DMTLAX. Verify that the RSCS virtual machine configuration has been correctly
specified and that the "retrieve subsequent file descriptor" function of DIAGNOSE Code X'14' is supported. Dump the contents of virtual storage
via the CP DUMP command. If the problem persists, notify the
installation support personnel. !AI! CODE An unrecoverable error occurred when reading the RSCS nucleus from DASD storage. This may be caused by a hardware
malfunction of the DASD. It may also be the result of an incorrect
virtual DASD definition, an attempt to use a system residence device
unsupported by RSCS, incorrect RSCS system generation procedures, or the
subsequent overwriting of the RSCS nucleus on the system residence
device. The wait state code is loaded by DMTINI after an attempt,
successful or not, to issue the message: DMTINI402T IPL DEVICE READ I/O ERROR Verify that the RSCS system residence device has been properly
defined as a virtual DASD and that the real DASD is mounted and
operable. If the problem persists, dump virtual storage via the CP DUMP command and notify the installation support personnel. The RSCS system
residence device may have to be restored or the RSCS system may have to
be regenerated.
Whenever RSCS has no task ready for execution, DMTDSP loads a masked-on
wait state PSW with a code of hexadecimal zeros. This occurs during
normal RSCS operation and does not indicate an error condition. An
external interrupt due to command entry or an I/O interrupt due to the
arrival of files automatically resumes processing.
Part 1. Debugging with VM/370 31