April 1, 1981
The START TAPE command starts the data collection by VK/370 Monitor onto a tape mounted on a 9-track tape drive. Specify "raddr" as the real hexadecimal address of the tape drive that
you want to use. It activates data collection for those
classes of MONITOR CALL previously specified in a KONITOR ENABLE command. The mask that was saved by the KONITOR ENABLE
command is moved into control register 8. The data is collected in two buffer pages in real storage. These pages
are separate from the internal trace table pages. As each
data page is filled, it is written onto the tape. Use BUFFS to specify the number of buffers to be used for
monit.orinq, where "nil may be 1 to 10 and specifies the number
of 4096-byte buffers to be used. If the option is omitted, VM/370 assigns a default. The value of the default depends
upon the model number or type of processor as follows: r -, Model or Processor Default I I Model 135, 138, or 145 2 buffersl I 4331 Processor 2 buffersl I Model 148, 155, or 158 3 buffersl I Model 165 or 168 4 buffersl I 3031, 3032, 3033, or I 4341 processor 4 buffersl It is valid to specify BUFFS 1 only if the PERFORM class of
data collection is the only one enabled with the MONITOR ENABLE command. Once monitoring is in progress with just one
buffer, it is not possible to issue a MONITOR ENABLE command
with other than just the PERFORM class of data collection
specified.
single-buffer operation is useful for basic performance
analysis in minimum main storage confiqurations. When the VM/370 Monitor is started, CP issues a REWIND command
followed by a Set Mode command for the reset value of tape
density.
The user can request a different mode setting by specifyinq
the MODE option in the MONITOR START TAPE command. Kode values of 800, 1600, or 6250 bpi may be specified. If a user specifies a density mode that the tape cannot
handle, the control unit may not return an error condition.
In this case, the mode setting is ignored, and the default
control unit settinq is used.
The START CPTRACE command starts the tracing of events that
occur on the real machine. The events are recorded in the CP internal trace t.able in chronological order. When the end of
the table is reached, recording continues at the beginning of
the table, overlayinq data previously recorded.
116 IBM System Programmer;s Guide

r ,1 STOP ISPOOL I i ICPTRACEI L CLOSE stops VM/370 Monitor data collection to a spool file or tape, or stops the CP internal trace If no option is
specified and the VM/370 Monitor is active, then data
collection is terminated, whether or not a spool file or tape
is in use. Internal tracing can only be stopped by specific
use of the CPTRACE option. If automatic VM/370 Monitor data
collection is active when the MONITOR STOP SPOOL command is
issued, monitoring ceases and will not start again (even if
the current time is within the bounds of the TIME operand of
the SISMON macro) unless the system abnormally terminates or
is shut down and reloaded.
The STOP TAPE command stops data collection by VM/370 Monitor onto tape. A zero mask is immediately stored in control
register 8, thus disabling MONITOR CALL The
last partially filled page is written out, two tape marks are
written, and the tape is rewound and unloaded. The two buffer
pages, which were obtained at the time the MONITOR START TAPE command was issued, are released.
The STOP CPT RACE command terminates the tracing of events
occurring on the real machine. Event recording ceases but the
pages of storage containing the CP internal trace table are
not released. Tracing can be restarted at any time by issuing MONITOR START CPTRACE. The CPTRACE and TAPE operands of the MONITOR command
have completely separate functions. Commands affecting the
status of one function have no effect on the other.
may be used when VM/370 Monitor is collecting performance data
using a spool file and it is desirable to reduce the data
collected thus far. The command closes the current spool file
(thereby making it available to the reader of the recipient
virtual machine) and causes monitoring to continue
uninterrupted with a new spool file. AUTOdisk {ON } OFF may be used to override the specification for automatic
monitoring in the SISMON macro. Its only use is to affect the
automatic startup of monitoring. If automatic monitoring is
already active, it may only be stopped manually by a MONITOR STOP command. Note that in general, any attempts to override
the definitions of the SISMON macro with commands are
temporary. No monitor checkpointing is attempted, so that an IPL or abnormal termination causes full restoration of the
initial automatic monitoring definitions.
lThe default value is the active trace facility that is SPOOL or TAPE. Part 2. Control program (CP) 117