Modifying duplexing characteristics

Use the Setcache Availability Entry panel to manage the availability of a duplex pair of devices that control the duplication and recovery of data. The AVAILABILITY characteristics affect only data that is on DASD.

To establish a duplex pair, you must specify:

A primary and a secondary device
The type of synchronization between the two devices

You can specify the rate of copy in the synchronization. Once duplexing is established, the storage control unit writes data to the primary device and simultaneously places a copy of it in cache along with control information in NVS. At a later time, the data in cache is written out to the secondary device, and the control information in NVS is updated.

If duplexing is interrupted, the dual copy pair is suspended. The storage control still writes information to NVS, but data is written to only the primary device. When duplexing is resumed, the secondary device is placed back in synchronization by the storage subsystem.

You also can use the Setcache Availability Entry panel to move the contents of one device to another. The panel allows you to establish a duplex-pair between two devices to copy data. The pair is immediately broken when all data has been copied. The original device is then available for maintenance.