The CP DEFINE command allows you to change your configuration
temporarily for the current terminal session. For example:
define reader OOb temporarily aids a card reader at virtual address OOB. The entry:
define t3330 as 291 cyl 125
adds a temporary virtual disk, containing 125 cylinders, at virtual
addr ess 291.
If your virtual machine is operating in basic control (B:) mode (that
is, your machine can use only six channels 0-5), you can only
define virtual devices with addresses up through 5FFi in extended
control (E:) mode, your virtual machine can use 16 channels O-F, and you
can use all addresses through FFF. You can enter:
define storage as 768k +0 temoorarily change the virtual storage size of your virtual machine 768K (K=1024 bytes). When you redefine storage, your virtual machine
is automatically reset and you must reload your operating system.
When Jsinq the SPOOL, SPECIAL and DEDICATE directory control statements to define virtual devices, specify virtual addresses that do
not with or contend with the virtual control unit interfacee This or contention occurs because devices can require special IIO interface protocols from control units such as shared and nonshared
subchannel operations. putting devices that require different real
control units on the same virtual control unit can result in a hung or busy To avoid this problem, users must define (and separate)
devices within their own control unit range. For example, if the
directory entry specifies: SPOOL 102 3211 SPECIAL 103 3270
the contr)l unit 0 on channel 1 controls both a nonshared device (the 3211 printer) and a shared device (the 3270 display unit). Processing
of both proqrams involving these two devices can result in a
hunq or busy condition=
Testing and Debugging of Programs
In to the testing and debugging facilities that are contained
in your virtual machine's operating system, has several CP commands that you can use. These commands can be used to locate,
display, and alter the program instructions that are executing in your virtual storage.
In the followinq discussions of the ADSrOp, DISPLAY, DUMP, and STORE commands, it is important that you understand the levels of storage you
can specify on the command line. Only first level storage (storage that is real to the virtual
machine) can be handled directly. This includes the V=R partitions or reqions of DOS/VS and OS/VS as well as storage in as/pcP, MFT, and MVT. V=V partitions or regions of DOS/VS and OS/VS constitute second
level st)rage and cannot be specified directly. The user, or the Section 3. CP Command Usage 27

virtual o?eratinq system, is responsible for converting any second level storage aldresses to first level storage addresses before including them
in the specific command line. STOPP1N3 EXECUTION OF YOUR VIRTUAL MACHINE
To stop execution of your virtual machine at a given address in virtual
storage, use the ADSTOP command and specify the hexadecimal address of a
virtual instruction. The command: #cp adstop 3000 stops the virtual machine when the instruction 3000 is the next instruction to be executed.
runninq, you receive the message: AT 3000 at hexadecimal location When the machine stops
and YO'lr terminal is placed in CP console function mode. At this point,
you can enter other CP debugging commands to display and alter storage or to tra=e certain instructions. When you want to resume running your
virtual machine, enter:
begin Unlike the hardware address stop, ADSTOP is turned off when: • The address is reached. • The next ADSTOP command is issued. • An 1PL or a system reset is performed. • The ADSTOP OFF command is issued. While is on, the SVC portion
executed. When ADSTOP is turned off,
machine assist. DISPLAYING VIRTUAL STORAGE of virtual machine assist is not SVcs are again handled by virtual contents of virtual storage, storage keys, general registers,
floating-point reqisters, control registers (if in EC mode), PSi, CAW, and CSW can be displayed on your terminal via the DISPLAY command. All
but the and csw can be printed on the Spooled virtual printer via
the ryUMP The DISPLAY and DUMP commands are fully described in Section 5. The
examples that follow do not attempt to show all possible uses.
TERMINAL OUTPUT With the DISPLAY command, you can display virtual storage at your
terminal in either of the following formats: • Four byte qroups, aligned on fullword boundaries, hexadecimal format, printel four fullwords per line. IB' VM/370 CP Command Reference for General Users