Class --0-- 1
2
3
4
5
6 RESPONSE SCHEDULE USER DASTAP !ungtiQn Samples system resource usage data by accessing
system counters of interest to system
performance analysts.
Collects data on terminal I/O. Simplifies
analyses of command usaqe. user. and system response times. It can relate user activity to
system performance. This class is invalid and
no data can be collected for it unless the
system programmer changes the LOCAL COpy file
and reassembles DMKMCC. Collects data about scheduler queue
manipulation, monitors flow of work through the
system, and indicates the resource allocation
strategies of the scheduler.
Reserved. Periodically scans the chain of in the
system, and extracts user resource utilization
and status data.
Records every virtual machine privileged
instruction handled by the control program (CP) • Because simulation of privileged
instructions is a major source of overhead,
this data may lead to methods of improving
performance.
If the VMA feature is active, the number of
privileged instructions that are handled by the
control program is reduced for those virtual
machines that are running with the feature
activated. Periodically samples device I/O activity counts
(SIOs), for tape and DASD devices only.
It is possible that the number of DASD and taFe
devices defined in DMKRIO may exceed 291 (the maximum number of MONITOR DASTAP records that
fit in a MONITOR buffer). The following
algorithm determines which devices are
monitored:
1. If the total number of DASD and tape
devices that are online is less than or
equal to 291, all online DASD and tape
devices are monitored.
2. If the total number of online DASD devices
is less than or equal to 291, all online
DASD devices are monitored.
3. Otherwise, the first
devices are monitored.
291 online DASD

Monitor 7
8 SEEKS SYSPROF Data Collection Function collects-aita -for-every I/O request to DASD. Reveals channel, control unit, or device
contention and arm movement interference
problems.
Note: When VIrtual=real collected. NOTRANS machine,
is in effect
no meaningful
for
data
a
is
No data is collected for TIO or HIO operations.
For SIO operations, data is collected when the
request for the I/O operation is initially
handled and again when the request is
satisfied.
This means that a single SIO request could
result in two MONITOR CALLs. For example, if
the request gets queued because the device is
already busy, then a MONITOR CALL would be
issued as the request is queued. Later, when
the device becomes free and is restarted, a
second MONITOR CALL is issued.
In general, the data collected is the same
except that in the first case there will be
nonzero counts associated with queued requests.
If the request for I/O is satisfied when it is
initially handled without being queued, only
one MONITOR CALL results. In both this case
and the second of the two data collections
mentioned above, the count of I/O requests
queued for the device is zero.
Collects data complementary to the DASTAP and SCHEDULE classes in order to provide a more
detailed "profile" of system performance
through a closer examination of DASD utilization. VM/370 MONITOR RESPONSE TO UNUSUAL TAPE CONDITIONS When I/O to the tape is requested, the device may still be busy from the
previous request. If this occurs, two data pages are full and data
collection must be temporarily suspended. Control register 8 is saved
and then set to zero to disable MONITOR CALL program interruptions and timer data collection. A running count is kept of the number of times
suspension occurs. The current Monitor event is disregarded. When the
current tape I/O operation ends, the next full data page is scheduled
for output. MONITOR CALL interruptions are reenatled (control register 8
is restored), a record containing the time of suspension, the time of
resumption, and the suspension count is recorded and data collection
continues. The suspension count is reset to zero when the MONITOR STOP TAPE is issued. Part 2. Control Program (CP) 121