When an I/O operation completes, an I/O interrupt occurs to signal the end of the operation. The MIH time interval is the period of time that the missing interrupt handler (MIH) waits before reporting that an expected interrupt from an I/O device is missing. At system initialization, MIH uses control statements in SYS1.PARMLIB to assign MIH time intervals to devices. If there is a missing interrupt, the system tries to resolve it and make the device usable again. It might clear the subchannel, end the operation, or try the operation again.
To retrieve the current MIH time interval for a device, use the MIHQUERY macro. This macro requires you to specify the address of the UCB or a copy of the UCB for the device. To determine the address of the UCB for a device, see Obtaining UCB information (general methods).