Dual Copy Device Address Mapping

In a dual copy environment, normal subsystem activities can modify the internal mapping of the system address (device number) to the actual device. In IDCAMS reports and in the output of the DEVSERV command, the low-order two digits of the system address are shown as the CCA, whereas the physical device address is shown as the DDC. The subsystem manages the integrity of this mapping, so it need not be a cause for concern. Circumstances exist, however, when the user needs to be aware that dual copy address mapping may have changed:

When device maintenance is required
When devices are being removed or repositioned
When subsystem re-initialization is required
When it is necessary to vary a device offline for reconfiguration or maintenance, use the CCA to determine the system address.

You can see the current map of system and device addresses by issuing the DEVSERV command or by running IDCAMS LISTDATA DSTATUS to any device or volume in the subsystem. Along with EREP (for 3380s) and SIM messages (for 3390s), this information may be useful to the service representative for identifying a failing device.

Note: Because of the asynchronous nature of IDCAMS operations, it is possible that during certain operations, the results from a DEVSERV command could differ from the results of an IDCAMS report. If the two operations start together, the DEVSERV results are more current.