Page of GC20-1807-7 As Updated April 1, 1981 by TNL GN25-0829 with eMS This section describes the debug tools that CMS provides. These tools
can be used to help you debug CMS or a problem program. In addition, a CMS user can use the CP commands to debug. Information that is often
useful in debugging is also included. The following topics are
discussed in this section: CMS debugginq commands Load maps Reading CMS dumps Control block summary CMS Debugging Commands CMS provides two commands that are useful in debugging: DEBUG and SVCTRACE. Both commands execute from the terminal.
The debug environment is whenever: The DEBUG command is issued A breakpoint is reached An external or program interrupt occurs CMS will not accept other commands while
However, while in the debug environment,
command can be used to:
in the debug environment.
subcommands of the DEBUG set breakpoints (address stops) that stop program execution at
specific locations. Display the contents of the CAW (channel address word), CSW (channel
status word), old PSW (proqram status word), or general registers at
the terminal. Change the contents of the control words (CAW, CSW, and PSi) and general registers. Dump all or part of virtual storage at the printer. Display the contents of . up to 56 bytes of virtual storage at the
terminal. store data in virtual storage locations. Allow an oriqin or base address to be specified for the program. Assign symbolic names to specific storaqe locations. Close all open files and I/O devices and update the master file
directory. Exit from the debug environment. 64_2 IBM VM/370 System programmer's Guide
The SVCTRACE command records information for all SVC calls. When the
trace is terminated, the information recorded up to that point is
printed at the system printer.
In addition, several CMS commands produce or print load maps. These
load maps are often used to locate storage areas while debugging
programs. DEBUG The DEBUG command provides support for debugging programs at a terminal. The virtual machine operator can stop the program at a specified
location in order to examine and alter virtual storage, registers: and
various control words. Once CMS is in the debug environment, the
virtual machine operator can issue the various DEBUG subcommands.
However, in the debug environment, all of the other CMS commands are
considered invalid.
Any DEBUG subcommand may be entered if CMS is
environment if the keyboard is unlocked. The following DEBUG subcommands:
1. No operand should be longer than eight characters.
longer than eight characters are left-justified and
the right after the eighth character.
in the debug
rules apply to
All operands
truncated on
2. The DEFINE subcommand must be used to create all entries in the DEBUG symbol table.
3. The DEBUG subcommands can be truncated. The following is a list of
all valid DEBUG subcommands and their minimum truncation. BREAK CAi CSi DEFINE DUMP GO GPR HI ORIGIN PSi RETURN SET STORE I Minimum !!Yll£g!i21l BR CAi CSW DEF DU GO GPR HI OR PSi RET
I One way to enter the debug environment is to issue the DEBUG command.
appears at the terminal. Any of the DEBUG subcommands may be entered.
To continue norma-l processing, issue the RETURN subcomm-and. ihenevera program check occurs, the DMSABN routine gains control. Issue the DEBUG command at this time if you wish CMS to enter the debug environment. Part 1. Debugging with VM/370 65
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