Displaying the status of devices and availability of paths

There are three commands that you can use to display the status of devices and the availability of the paths these devices are on.

This command displays device status and the job names and ASIDs of device users. Knowing what jobs and ASIDs are using a particular device allows you to determine whether you can take the device offline. See Displaying device status and allocation for information about the DISPLAY U command.

The DISPLAY M command allows you to keep track of the availability of channel paths and devices on these paths. See Displaying system configuration information for information about the DISPLAY M command.

The DEVSERV PATHS command can help you solve hardware or configuration problems. The display includes the status of paths, the channel path ids, the logical mode of devices, the number of data sets allocated on volumes, and volume serial labels. Because the DEVSERV command causes the system to issue an I/O request on paths to a device or devices, the resulting display reflects the current physical state of the path. Comparable displays from the DISPLAY M command reflect less recent information from the last use of MVS™ control blocks. For example, assume that an I/O device is performing below normal and you suspect that some paths to the device are offline. The DISPLAY M command might tell you that there are four paths online to the device. The DEVSERV PATHS command might tell you that there is actually only one online path. The DEVSERV command is more current and thus more accurate. See DEVSERV command for information about the DEVSERV command.