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Before an Oracle database changes data in a datafile it writes changes to the redo log. If something happens to one of the datafiles, a recovery procedure can restore a backed-up datafile and then replay the redo written since backup-time; this brings the datafile to the state it had before it became unavailable.
Minimizing downtime and data loss during disaster recovery is typically measured in terms of two key concepts: Recovery time objective (RTO), time until a system is completely up and running; Recovery point objective (RPO), a measure of the ability to recover files by specifying a point in time the backup copy will restore to.
Time Machine for Mac OS X provides another example of point-in-time recovery. Once PITR logging starts for a PITR-capable database , a database administrator can restore that database from backups to the state that it had at any time since.
Search and Recover can rescue crucial work and cherished memories you thought were gone forever. It's fast and easy to use, and even data lost years ago can be recovered.
The most common data recovery scenarios involve an operating system failure, malfunction of a storage device, logical failure of storage devices, accidental damage or deletion, etc. (typically, on a single-drive, single-partition, single-OS system), in which case the ultimate goal is simply to copy all important files from the damaged media to another new drive.
An effective backup strategy must also consider the cost of maintaining the ability to recover lost data for long periods of time. A highly effective backup system would have duplicate copies of every file and program that were immediately accessible whenever a Data Loss Event was noticed. However, in most situations, there is an inverse ...
ASM creates extents out of datafiles, log-files, system files, control files and other database structures. The system then spreads these extents across all disks in a "diskgroup". One can think of a diskgroup in ASM as a Logical Volume Manager volume group — with an ASM file corresponding to a logical volume.
A database dump contains a record of the table structure and/or the data from a database and is usually in the form of a list of SQL statements ("SQL dump"). A database dump is most often used for backing up a database so that its contents can be restored in the event of data loss. Corrupted databases can often be recovered by analysis of the dump.