to a remote location via the Remote Spooling Communications Subsystem,
RSCS expects to find the destination identification in the file tag. Tag
data is set, changed, and queried using the CP TAG It to spool terminal input and output. All data sent to
the terminal, whether it be from the virtual machine, the control
program or the virtual machine operator, can be spooled. Spooling is
particularly desirable when a virtual machine is run with its console
disconnected. Console spooling is usually started via the command SPOOL CONSOLE START An exception to this is when a system operator logs on using a graphics
device. In this instance, console spooling is automatically started and
continues in effect even if the system operator should disconnect from
the graphics device and log on to a nongraphic device. In order to stop
automatic console spooling, the system operator must issue the command SPOOL CONSOLE STOP SPOOL FILE RECOVERY If the system should suffer an abnormal termination, there are three
degrees of recovery for the system spool files; warm start (WARft), checkpoint start (CKPT), and force start (FORCE). Warm start is
automatically invoked if SET DUMP AUTO is in effect. Otherwise, the
choice of recovery method is selected when the following message is
Bote that a cold (COLD) start does not recover any spool files. After a system failure, the warm start procedure copies spool file,
accounting, and system message data to warm start cylinders on an
auxiliary DASD. When the system is reloaded, this information is
retrieved and the spool file chains and other system data are restored
to their original status. If the warm start procedure cannot be
implemented because certain required areas of storage are invalid, the
operator is notified to take other recovery procedures.
Any new or revised status of spool file blocks, spooling devices, and
spool hold queue blocks is dynamically copied to checkpoint cylinders on
an auxiliary DASD as they occur. When a checkpoint (CKPT) start is
requested, this is the information that is used to recreate the spocl
file It differs from warm start data in that only spool file
data is restored; accounting and system messages information is not
recovered. Also, the order of spool files on any particular restored
chain is not the original sequence but a random one. Part 2. Control Program (CP) 81
A force start is required when checkpoint start encounters I/O errors
while reading files, or invalid data. The procedure is the same as for
cbeckpoint start except that unreadable or invalid files are bypassed. CP The CP commands allow you to control the virtual machine from the
terminal, much as an operator controls a real machine. Virtual machine
execution can be stopped at any time by use of the terminal's attention
key (for 3066 and 3270 terminals, the ENTER key is used); it can be
restarted by entering the appropriate CP command. External, attention,
and device ready interrupts can be simulated on the virtual machine. Virtual storage and virtual machine registers can be inspected and
modified, as can status words such as the PSi and the CSW. Extensive
trace facilities are provided for the virtual machine, as well as a
single-instruction mode. Commands are available to invoke the spooling
and disk sharing functions of CP. CP commands are classified by privilege classes. The V8/370 directory entry for each user assigns one or more privilege classes.
The classes are primary system operator (class A), system resource
operator (class B), system programmer (class C), spooling operator
(class D), system analyst (class E), service representative (class F),
and general user (class G). Commands in the system analyst class may be
used to inspect real storage locations, but may not be used to make modifications to real storage. Commands in the operator class provide
real resource control capabilities. System operator commands include
all commands related to virtual machine performance options, such as
assigning a set of reserved page frames to a selected virtual machine.
For descriptions of all the CP commands, see the !£f and the 82 IBM VM/370 System Programmer's Guide
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