To enter a CP command while the DOS/VS virtual machine is in operation, press the attention key (or its equivalent) twice, quickly,
to force a CP read. After entering the necessary CP commands, use the CP BEGIN cemmand to resume DOS/VS virtual machine execution. For example: If a DOS/VS PAUSE control statement requests the VM/370 cFerator tc Ferform some action, the user must enter the CP environment
to send a message to the VM/370 system operator. The following lines
represent a typical sequence on a typewriter terminal:
// PAUSE ASK OPERATOR TO ATTACH TAPE AS 284
! ! CP msg op please attach scratch tape as 284
sleep TAPE 284 ATTACHED CP begin
The SLEEP command locks the keyboard and places the virtual machine in a
dormant status to wait for any messages,. When the message appears
indicating the tape is attached, press the attention key once to return
to CP, and then issue the BEGIN command to resume virtual machine
execution. Because the // PAUSE message is still outstanding, press the RETURN key to continue DOS/VS execution.
In most cases during virtual machine operation, use the 'CP function to
enter CP commands directly from the virtual machine environment. Users de not always have to press the attention key (or its equivalent) to
enter the CP environment. For example: If the virtual machine is
waiting for a read, a user can enter a CP command with the ICP function: #cp msg op please mount vo1240
The command line is processed by VM/370, and the virtual machine is
still waiting for a read. This method may be convenient for entering CP commands.
Note: At times CP commands cannot be entered with the ICP function. For exiiple: During the IPL procedure when DOS/VS is processing 1FL commands, the CCis used for these reads expect only three bytes of
data. Any additienal information on CP command lines is truncated. While DOS/VS is running in the virtual machine, a user can interrupt its
execution by using the attention key (or its equivalent) on the
terminal. When this key is pressed, the DOS/VS attention handler
responds with these messages:
AR 1I60A READY FOR COMMUNICATIONS. AR When these messages appear, a user can enter attention commands. To
resume program execution, enter a null line. Normally, wait until the
attention has been processed before signaling another one. An exception
would be when canceling a dump.
92 IBM VM/370 Operating Systems in a Virtual Machine
When using a 2741 terminal and its attention key mainly to signal CP interruptions, enter the command: tcp terminal mode cp
The first time the attention key is pressed, VM/370 posts a CP interruption. The next pressing of the attention key signals an interruption to DOS/VS. When a user is in the CP environment and wants
to signal an interruption to DOS/VS, enter either the ATTN or REQUEST commands.
Running Batch DOS/VS Under VM/370 When using DOS/VS in a virtual
likely that the virtual machine
continuously. This machine may
jobs, or it may be used only by running the production jobs. machine as a production tool, it is
running DOS/VS is going to be logged on
be available for many users to submit
installation personnel responsible for
In either event, it is likely
sFecifically for use under VM/370. whether:
that DOS/VS has been generated
In this case, a user should know It is necessary to start more than one partition. If it is,
determine how much virtual storage to allocate to each partition.
These considerations are much the same as they would be for a native DOS/VS user, who must decide how much work is going to be done and
what is the most efficient way to do it. To generate the POWER program (POWER/iS for DOS/iS or VSE/PCWER for DOS/VSE). This program can provide many functions that are not
available when relying solely on CP spooling, such as spooling jobs
via class and purging ,selected jobs in a job stream. When the POWER program is active in the 'DOS/VS virtual machine, it
controls which jobs are to be processed in the various partitions,
and it reads jobs from the card reader. Because the program is
constantly working, no need exists for an attention interruption
when a new job is placed in a card reader. To start the POWER program in a virtual machine, use the AUTOSTABT procedure. Enter the card deck for the automatic start either using
cards in the reader or through the virtual card reader. Virtual devices are dedicated for use by the DOS/VS virtual machine
or devices must be shared among other virtual machines.
For example: If a card reader has been dedicated to a DOS/VS virtual
machine, then users may submit jobs through that card reader. They
de not have to place a CP ID card at the beginning of the deck to
direct it to the appropriate virtual machine. If the DOS/VS virtual
machine is sharing the system card reader, then any user submitting a card deck must place a CP ID card at the beginning of the deck,
sFecifying the userid of the DOS/VS virtual machine. Section 3. DOS/VS in a Virtual 93
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