I. Description of the problem
Background note, Dg prepared by the library needs to be restored to three days ago, but did not open during the flashback, temporary start, the emergence of this mistake. Cause Analysis:
To enable Flashback Database, you configure a fast recovery area and set a flashback retention target. This retention target specifies how far back you can rewind a database with Flashback Database. From that time onwards, at regular intervals, the database copies images of each altered block in every data file into the flashback logs. These block images can later be reused to reconstruct the data file contents for any moment at which logs were captured. When you use Flashback Database to rewind a database to a past target time, the command determines which blocks changed after the target time and restores them from the flashback logs. The database restores the version of each block that is immediately before the target time. The database then uses redo logs to reapply changes that were made after these blocks were written to the flashback logs. Redo logs on disk or tape must be available for the entire time period spanned by the flashback logs. For example, if the flashback retention target is 1 week, then you must ensure that online and archived redo logs that contain all changes for the past week are accessible. In practice, redo logs are typically needed much longer than the flashback retention target to support point-in-time recovery. During the flashback operation, RMAN may need to restore archived redo logs from backup. Enter the following command to see whether channels are configured (sample output is included):
This is the official document describes the redo logs to restore to the point specified period of time to ensure that there is, for example, if the flashback retention target one week, you must ensure that access to include all online and archived redo log changes of the past week. In practice, redo logs are usually longer than the flashback retention target to support point in time recovery. So the question may arise archive missing, or is temporarily turned flashback, but this did not hold any recovery operation.