It is possible to spool ter.inal 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 com.and 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; war. start (WAR!), checkpoint start (CKPT), and force start (FORCE). Warm start is
automatically invoked if SET DU!P AUTO is in effect. Otherwise, the
choice of recovery method is selected when the following message is
issued; hh:mm:ss STIRT «COLDIWAR!ICKPTIFOBCE) (DRAII)) I (SHUTDOWN): 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 spool
file chains •. It differs from warm start data in that only spool file
data is restored; accounting and system messages information is not
recovered. Ilso, the order of spool files on any particular restored
chain is not the original sequence but a random one.
1-8 IB! V8/310 System Logic and Problem Determination--Volume 1

A force start is required when checkpoint start encounters I/O errors
while reading files, or invalid data. The procedure is the saae as for
checkpoint start except that unreadable or invalid files are bypassed.
CP COMMANDS The CP commands allow you to control the virtual machine froa the
terainal, much as an operator controls a real aachine. Virtual machine
execution can be stopped at any time by use of tbe terminal
1
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 siaulated on the virtual aachine.
Virtual storage and virtual machine registers can be inspected and
.odified, as can status words such as the PSi and the CSi. 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 com.ands are classified by privilege classes. The VM/370 directory entry for each user assigns one or more privilege classes.
The classes are primary systea operator (class A), system resource
operator (class B), system progra.aer (class C), spooling operator
(class D), system analyst (class E), service representative (class P), 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 aodifications to real storage. Co.mands in the operator class provide
real resource control capabilities. System operator commands include
all coamands related to virtual aachine performance options, such as
assigning a set of reserved page frames to a selected virtual aachine. Par descriptions of all the CP commands, see the 1M/370 fo!: General and the V!!/370 CP Introduction 1-9