Do you know, what the z/VSE MIH does ?
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The MIH (Missing Interrupt Handler) is a z/VSE Supervisor routine, that gets control regularly. It verifies, if a device did not complete an I/O after a defined time interval. The I/O Supervisor will then try to determine, why the device did not answer. An appropriate message may be written to the z/VSE console. If the device is in error, a record will be written to the recorder file too.
You may set the time interval with the Attention Routine SIR MIH command and enable or disable the MIH process in z/VSE. The time interval may be set for a single device or in general for all devices. SIR MIH without any parameter displays the general MIH settings. By default the MIH is enabled and the time interval 3 minutes. That is z/VSE waits for at least 3 minutes, if an I/O does not complete, until it writes an (action) message (0E02t DEVICE cuu LOST CHAN+DEV END) to the z/VSE console.
The time interval depends on the interrupt timing of your devices, e.g. tape devices need longer intervals than a disk / DASD device. In most cases there is no need to change the defaults. If you see message 0E02t and it's not a device error, you may need to adapt the MIH time interval. If you don't want to wait three minutes (default) in case of an I/O problem and you know that your devices can handle interrupts much faster, you may reduce the time interval.
More details are in the Hints and Tips for z/VSE 5.1 book on our z/VS
Have a good weekend.