The two-phase recovery process
In the two-phase recovery method, the Recovery utility restores the database data set from a standard image copy or supported non-standard image copy and then applies change accumulation and sorted log records.
In a two-phase recovery, the Recovery utility concurrently sorts log records while restoring the database. In a single-phase recovery, the Recovery utility must wait for the log sorting to complete before it can start writing the merged database records to DASD. Therefore, a two-phase recovery can be faster than a single-phase recovery in some cases, particularly if the input image copy is an Instant Snapshot copy produced by the BMC Image Copy utility.
The Recovery utility performs a two-phase recovery automatically when it detects that the input image copy is an Instant Snapshot copy produced by the BMC Image Copy utility or is a T0 copy produced by the Data Base Image Copy 2 utility from IBM. The SNAPSHOT UPGRADE FEATURE (SUF) component works with intelligent storage devices to restore an Instant Snapshot copy nearly instantaneously. You specify the XBMSSID keyword to identify the XBM subsystem to use.
Although it is normally unnecessary to do so, you can identify that the input image copy is an Instant Snapshot copy or is a T0 copy by specifying the DUMPTYPE keyword on a control statement.
You can request a two-phase recovery explicitly for all DBDs in the job step by specifying the RESTORE keyword on a control statement.
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