An Overview of VM/SP Commands that Can Be Used for Debugging
The VM/SP Control Program provides interactive commands that control the VM/SP system and enable the user to control his virtual machine and associated
control program facilities. The virtual machine operator using these commands can
gather much the same information about his virtual machine as the operator of a
real machine gathers using the processor console. Several of these commands (for example, STORE or DISPLAY) examine or alter
virtual storage locations. When CP is in complete control of virtual storage (as in
the case of DOS, MFT, MVT, PCP, CMS, and RSCS) these commands execute as
expected. However, when the operating system in the virtual machine itself manip­
ulates virtual storage (as in the case of OS/VSl, OS/VS2, or DOS/VS) these CP commands should not be used.
This section presents an overview of the VM/SP commands used for debugging. It
supplements the preceding section which discussed debugging procedures and tech­
niques. Instructions for using the commands discussed in this section are in the fol­
lowing publications: • VM/SP CP Command Reference for General Users • VM/SP Operator's Guide • VM/SP CMS Command and Macro Reference
The following categories of commands are discussed:
Commands that display VM/SP control information
Commands that set and query system features, conditions, and events
Commands that collect and analyze system information
Commands that trace events in virtual machines
Commands that alter the contents of storage
Commands that Display or Dump Virtual Machine Data
Commands that display or dump virtual machine data are: DUMP, VMDUMP, DISPLAY, DCP, and DMCP. The DUMP and DISPLAY commands of CP are privilege class G commands and
are used to display control information describing the status of virtual machines.
The DUMP command spools the following information to your virtual printer: • Virtual program status word (PSW) • General registers
Floating-point registers • Control registers (if your VM/SP directory has the ECMODE option) Storage keys
Virtual storage locations (first-level storage only)
The DISPLAY command displays at your terminal the following kinds of control
information:
Virtual storage locations (first-level storage only) • Storage keys . General registers
Floating-point registers
Introduction to Debugging 497

Control registers
Program status word (PSW) • Channel address word ( CAW)
Channel status word (CSW)
The DCP and DMCP commands of CP are privilege class C and E commands and
are used to display real storage locations. The DMCP command spools the con­
tents of real storage to your virtual printer. The DCP command displays at your
terminal the contents of real storage locations.
The class G VMDUMP command dumps virtual storage to a specified reader spool
file. VMDUMP provides the same dump information that the DUMP command
provides but in a different format. For example, if a byte of storage contains X'OO', DUMP records it in printable format, X'FOFO'; VMDUMP records it as it
appears in storage, X'OO' The VM/Interactive Problem Control System Extensions
program product can process records written by VMDUMP. For a description of
the format and contents of the VMDUMP records, see "VMDUMP Records:
Format and Content" in this section.
Commands that Set and Query System Features, Conditions, and Events
The SYSTEM and SET commands set system-controlled functions and events; the
QUERY command allows you to determine the status of those settings.
The SYSTEM command is a privilege class G command that simulates the RESET
and REST ART buttons on a real computer console. It can also be used to clear
storage.
The functions of the SET command are described in detail in the VM / SP CP
Command Reference for General Users. For debugging, the SET command provides
the MSG, WNG, and EMSG operands. These provide messages that may be useful
while you are debugging.
The SET MSG function determines whether you receive messages sent by other
users via the MSG command. Also, the MSG operand determines whether you
receive messages from CP when other users spool reader, printer, or punch files to
your virtual machine.
The SET SMSG command turns on or off a virtual machine's special message flag.
If the virtual machine has issued DIAGNOSE Code X'68' (Authorize), this flag
determines whether the virtual machine accepts or rejects messages sent via the SMSG command --when the flag is on, messages are accepted.
The SET WNG function determines whether you receive warning messages from
the system operator.
The SET EMSG function controls error message handling. The EMSG operand
gives you the ability to specify that you want message code, message text, or both
to be displayed at your terminal. You can also specify that no messages be dis­
played (except in the case where you have spooled your console output).
When you are debugging, it is useful to have all messages displayed at your termi­
nal.
The QUERY command displays the status of features and conditions set by the SET command for your virtual machine. When you logon, the MSG and WNG
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