RMAN uses the recovery
catalog--or target database control file if no recovery catalog is
available--to select the best available backup sets for use in the
restore operation. When multiple choices are available, RMAN uses
the most current backup sets, taking into account whether you
specified any limits.
By selecting Restore from the most recent backup sets, RMAN
selects the most current backup set to restore.
Selecting Restore from backup sets limited by limits the
selection to those backup sets that would be suitable for
performing a point-in-time recovery.
The upper limit may be
specified by time, SCN, or log sequence number, as follows:
Specifies a time as an upper limit
System Change Number
Specifies an SCN as an upper limit
Log sequence number
Specifies a redo log sequence number as an upper limit
Indicates the thread number for the redo log in question