Non-concurrent image copies

Non-concurrent image copies are image copies that are taken while no updates are being made to the database.

Non-concurrent image copies are also referred to as batch image copies, because they are often created when the database is offline, or clean image copies because they do not contain any fuzzy data. All of the data reflected in the image copy has been committed and the image copy by itself can be used as the starting point for recovery. Only log records for updates to the data set that occur after the image copy is made are needed to recover the data set.

You can create non-concurrent image copies in two ways:

• By quiescing the database, area, or partition with the quiesce and hold option specified and running one of the image copy utilities. Databases, areas, and partitions are held in the quiesce state by issuing the appropriate UPDATE command with the START(QUIESCE) OPTION(HOLD) keywords. If a batch image copy utility is used, the DD statement for the database must specify DISP=SHR. After the image copy is complete, the quiesce must be released with another UPDATE command with the STOP(QUIESCE) keyword specified.
• By taking the database offline and running a batch image copy utility. This method requires stopping access to the database, deallocating it, and unauthorizing it with DBRC by issuing the appropriate UPDATE command with the STOP(ACCESS) keyword specified.

Of the two methods for creating non-concurrent image copies, using the quiesce function is the easier and faster method; however, because application programs are held in their dependent regions in a wait state, databases should be held in the quiesce state only during periods of low database activity.