Area data set replication

A data set can be copied, or replicated, up to seven times, increasing the availability of the data to application programs.

The DEDB Area Data Set Create utility (DBFUMRI0) produces one or more copies of a data set representing the area without stopping the area. All copies of an area data set must have identical CI sizes and spaces but can reside on different devices. The utility uses all the current copies to complete its new data set, proceeding to another copy if it detects an I/O error for a particular record. In this way, a clean copy is constructed from the aggregate of the available data. Current updates to the new data set take effect immediately.

The Create utility can create its new copy on a different device, as specified in its job control language (JCL). If your installation was migrating data to other storage devices, then this process could be carried out while the online system was still executing, and the data would remain current.

To ensure all copies of a DEDB remain identical, IMS updates all copies when a change is made to only one copy.

If an ADS fails open during normal open processing of a DEDB with multiple data sets (MADS), none of the copies of the ADS can be allocated, and the area is stopped. However, when open failure occurs during emergency restart, only the failed ADS is unallocated and stopped. The other copies of the ADS remain available for use.