Terminating error

A terminating error condition is unexpected only; it is never the result of a previous recovery action. A terminating error condition indicates that the channel path is not permanently lost, but cannot be used until the error condition is reset. In this case, the system attempts to reset the channel path. The CRW that results from this reset is an expected CRW, and it will indicate whether the reset corrected the problem in the channel path.

For a failing channel path that has a device with an outstanding reserve, the system handles the condition in three different ways, depending on whether the device supports dynamic pathing, supports unconditional reserve, or does not support unconditional reserve. The system actions are:

For a dynamic pathing device with multiple paths, no action is taken until the expected CRW is received.
For a non-dynamic pathing device that supports unconditional reserve, such as a 3350 Direct Access Storage, the system issues an unconditional reserve command to the device to move the reserve to an alternate path.
For a non-dynamic pathing device that does not support unconditional reserve, such as a 3330 Disk Storage, or for a reserved/assigned device with only one path, the system issues message IOS063E (or IOS062E) to request that the operator stop I/O to the shared devices (see Figure 1 and the accompanying description). The system then tries to recover the channel path.

Note: Since stopping I/O to shared devices may require a certain level of multi-system disruption and coordination, users may wish to avoid this processing. Through the use of the TERMINAL BOX_LP(device_class1,...device_classN) statement in the IECIOSxx Parmlib member, users can cause devices in the specified device class to be BOXED rather than having to undergo multi-system disruption to recover the channel path to the device. For more information on the use of the TERMINAL statement in IEAIOSxx, see z/OS MVS Initialization and Tuning Reference .

Figure 1. DASD Devices shared between two systems

The graphic depicts two systems sharing two DASD devices.

Figure 1 shows two DASD devices that are shared between two systems. When system 1 encounters a channel path error on channel path 01, indicated by message IOS063E (or IOS62E), the operator should stop I/O to the shared devices from system 2 to maintain data integrity during recovery of the channel path.