Monitor 7
8SEEKS 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 forTIO or HIO operations.
ForSIO operations, data is collected when the
request for theI/O operation is initially
handled and again when the request is
satisfied.
Thismeans that a single SIO request could
result in twoMONITOR CALLs. For example, if
the request gets queued because the device is
already busy, then aMONITOR CALL would be
issued as the request is queued. Later, when
the device becomes free and is restarted, a
secondMONITOR 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 forI/O is satisfied when it is
initially handled without being queued, only
oneMONITOR CALL results. In both this case
and the second of the two data collections
mentioned above, the count ofI/O requests
queued for the device is zero.
Collects data complementary to theDASTAP and SCHEDULE classes in order to provide a more
detailed "profile" of system performance
through a closer examination ofDASD 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 disableMONITOR 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 tapeI/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 theMONITOR STOP TAPE is issued. Part 2. Control Program (CP) 121
8
contention and arm movement interference
problems.
Note:
is in effect
no meaningful
for
data
a
is
No data is collected for
For
request for the
handled and again when the request is
satisfied.
This
result in two
the request gets queued because the device is
already busy, then a
issued as the request is queued. Later, when
the device becomes free and is restarted, a
second
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
initially handled without being queued, only
one
and the second of the two data collections
mentioned above, the count of
queued for the device is zero.
Collects data complementary to the
detailed "profile" of system performance
through a closer examination of
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
suspension occurs. The current Monitor event is disregarded.
current tape
for output.
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