Concurrent image copies

IMS allows you to create image copies of databases that are registered with DBRC while the database is being updated.

An image copy taken while a database is being updated is called a concurrent image copy or, because the copy represents the state of the database over a period of time rather than at an instant in time, a fuzzy image copy. When you create a concurrent image copy, your final copy might include some, all, or none of the updates made to a database during the copy process.

The IMS Database Image Copy 2 utility (DFSUDMT0) provides a concurrent copy option, which you should not confuse with a concurrent image copy. The concurrent copy option of the DFSUDMT0 utility can create either concurrent image copies or clean image copies. The concurrent copy option of the DFSUDMT0 utility takes its name from the CONCURRENT keyword of the z/OS® DFSMSdss DUMP command and does not refer to the type of image copy the option creates. DFSMS and the Concurrent Copy feature of 3990 hardware can make copies of a data set while the data set is offline or online.

The fast replication option of the DFSUDMT0 utility can also create either concurrent or clean image copies.

Restrictions: 

• The IMS image copy utilities can make a concurrent image copies only of databases that are registered with DBRC.
• You can make copies of nonrecoverable databases, but they must be stopped before you run the utility to make the image copies. You cannot take concurrent image copies of nonrecoverable databases while they are online because IMS does not log changes to them. The database itself becomes fuzzy if a fuzzy image copy of a nonrecoverable database is used to recover the database.
• Using the Database Image Copy utility (DFSUDMP0), you can only make concurrent image copies for OSAM and VSAM Entry Sequenced Data Set (ESDS) DBDSs; VSAM Key Sequenced Data Set (KSDS) DBDSs are not supported for concurrent image copy. If you use either of the other two image copy utilities, you can create image copies of ESDSs or KSDSs.