Using concurrent copy

Many online databases must be available at all times. If a backup is made while the data is being updated, the backup could be unusable or could require that a log be applied to the restored version to synchronize the data. The alternative is to synchronize all parts of the database and stop all update activity during the backup.

The concurrent copy (CC) function of DFSMSdss is a hardware and software solution that allows you to back up a database or any collection of data at a point in time and with minimum down time for the database. The database is unavailable only long enough for DFSMSdss to initialize a concurrent copy session for the data, which is a very small fraction of the time that the complete backup will take. The copy that is made will not include any of the update activity; it will be as if the backup were made instantaneously when it was requested. After initialization, DFSMSdss releases all the serialization it holds on the data, informs the user that the initialization is complete so that update activity may resume, and begins reading the data.

Be aware, however, that concurrent copy does not remove all data integrity exposures. For example, a DFSMSdss full-volume dump serializes the VTOC of the source volume, but does not serialize the data sets on the volume. This ensures that the existing data sets are not deleted or extended, and new data sets are not allocated. However, there is an exposure in that the data in the existing data sets can be changed. Without concurrent copy, this exposure exists for the entire duration of the dump. With concurrent copy, the exposure exists only during initialization.

Note:

If you are using concurrent copy on VM-format volumes, DFSMSdss does not serialize VM data in any way.
VM minivolumes are supported if you are using RAMAC Virtual Array (RVA) devices to the extent that they are supported by IBM® Extended Facilities Product (IXFP) device reporting.

If a dump requestor does not stop all updating of the data sets during the concurrent copy session initialization, the backup data integrity is compromised.

If a concurrent copy operation fails after signaling that the concurrent copy initialization was complete (and update activity on the data has resumed), it is not possible to recover the data at the point-in-time at which the concurrent copy operation was started. This is because the data may have been updated while the copy operation was progressing.