gtpo1m0e | Operations |
If a performance loss or system failure occurs, it may be desirable to operate at a less efficient level rather than changing back to switchover procedures.
You can perform manual fallback procedures for all hardware devices by issuing a command from a designated CRAS terminal. There are also some automatic fallback procedures. To fall back manually, you can change device assignments from any valid CRAS terminal. Automatic fallback is provided for the prime CRAS, RO CRAS, and tape devices. The switching, in this case, is automatically controlled by the system and you are informed of the action that is taken.
For DASD, you can perform a control unit fallback by using the module status change command program and moving each affected module to a different control unit.
Manual and automatic procedures exist for communication device and line fallback. Manual fallback is performed by entering a command from a CRAS terminal. Automatic fallback for the system console is performed by monitoring online errors and device traffic. When excessive error conditions occur, an alternate CRAS device is assigned. There is no automatic fallback for communication devices and lines other than prime and RO CRAS. A defective device is automatically taken offline and you are notified. You can manually assign any alternate device using a command. If there are no unimpaired devices on a line, the line is taken offline automatically. A line stays active as long as there is one device running on it.