Devices Monitored
Default Time Interval Values
- or- • The condition is pending
This message warns the system operator or system programmer that a problem may
exist. The system operator or the system programmer can reset the hardware and
schedule maintenance for the device that caused the missing interrupt condition. If
the same device class caused frequent interruptions, the system programmer may
want to set a larger time interval for that particular device class.
The class G SET command can be used to turn MIH on and off. Use either SET MIH ON or SET MIH OFF To determine the status of MIH use
QUERY SET The system responds either
MIH ON or MIH OFF Each device group has an expected time interval during which an I/O operation
should be completed. This interval varies widely among devices. Therefore, the
missing interrupt handler provides a means to specify a time interval for the follow­
ing distinct categories of I/O devices: • Count-key-data devices (CLASDASD) and FB-512 devices (CLASFBA)
Tape devices (CLASTAPE) • Graphic devices (CLASGRAF) except TYPI053 and TYP328X • Unit record devices (CLASURI and CLASURO) except TYP3800 and TYP3289E • Miscellaneous devices (MISC) include: Mass storage system (MSS) devices
(specified at system generation as CLASSPEC TYP3851, and CLASDASD FEATURE = VIRTUAL or FEATURE=SYSVIRT), graphics devices TYPI053 and TYP328X, and UR output devices TYP3800 and TYP3289E. Note: The missing interrupt handler does not support terminal devices, remote
graphic devices, SNA devices, pass-through virtual machine (logical) devices, and
special class devices (with the exception of MSS). Default time interval values are assembled in DMKSYS. The following table gives
the default time interval values for the devices monitored:
Interruption Handling 19

Changing the Time Interval
Device Class Default
Class Parameter Time Interval CLASDASD or CLASFBA DASD 15 seconds
CLASGRAF GRAF 30 seconds CLASTAPE TAPE 10 minutes CLASURI/ CLASURO DR 1 minute MISCELLANEOUS MISC 12 minutes
An installation may want to change the default time intervals because of their par­
ticular configuration. For example, an installation that generates a large number of
devices might want to set the time interval value to a larger number to prevent fre­
quent timer interruptions.
The system programmer or the system operator can change the time interval in the
following ways:
Regenerate the system and, using the SYSMIH macro, specify a time interval
value in the system control file (DMKSYS) for the specific device class to be
changed. Specify the time interval value in minutes and seconds: SYSMIH GRAF=00:15,UR=00:00,TAPE=05:00 This example changes the time interval for graphic devices from the default
value of thirty seconds to fifteen seconds. In this example, no further monitor­
ing takes place for unit record devices since the user specified a time value of
zero for that class. In addition, the example changes the time interval value for
tape devices from ten minutes to five minutes. This example does not change
the time interval value for DASD and MISC devices. If you do not specify a
device class, or if you do not include the SYSMIH macro in DMKSYS, the
missing interrupt handler uses the default value for that class. • To change the value specified in DMKSYS for a particular device class, issue
the class B CP command specifying the new time interval value for that class in
minutes and seconds: SET MITIME GRAF 00:10 This example changes the time interval for graphic devices to ten seconds.
This change is in effect until the system is reinitialized, or until a class Buser
issues another SET MITIME command. If the user specifies a time value of
zero for a specific device class, no further monitoring takes place for that
device class.
Note: If you set the time interval for a device class below its default value, be
careful not to shorten the time interval too much. This may cause unnecessary
missing interruption handler processing for devices that are functioning proper­
ly. • To set all time values to zero and to prevent any monitoring for missing inter­
rupts for any devices, issue the class B CP command: SET MITIME OFF 20 VM/SP System Programmer's Guide