Media Recovery Media recovery is used to recover a lost or damaged current datafile or control file. You can also use it to recover changes that were lost when a datafile went offline without the OFFLINE NORMAL option. Restoring Files When you restore a file, you are replacing a missing or damaged file with a backup copy. Recovery of Files When you recover a file, changes recorded in the redo log files are applied to the restored files. | User-Managed Complete Recovery Objectives After completing this lesson, you should be able to do the following: Describe media recovery Perform recovery in NOARCHIVELOG mode Perform complete recovery in ARCHIVELOG mode Restore datafiles to different locations Relocate and recover a tablespace by using archived redo log files Describe read-only tablespace recovery Media Recovery Used to recover a lost or damaged current datafile or control file Requires explicit invocation Operates as follows: Files are restored from backups Redo data is applied to the restored files from archived redo log files and online redo logs Media Recovery Media recovery is used to recover a lost or damaged current datafile or control file. You can also use it to recover changes that were lost when a datafile went offline without the OFFLINE NORMAL option. Restoring Files When you restore a file, you are replacing a missing or damaged file with a backup copy. Recovery of Files When you recover a file, changes . | User-Managed Complete Recovery Objectives After completing this lesson, you should be able to do the following: Describe media recovery Perform recovery in NOARCHIVELOG mode Perform complete recovery in ARCHIVELOG mode Restore datafiles to different locations Relocate and recover a tablespace by using archived redo log files Describe read-only tablespace recovery Media Recovery Used to recover a lost or damaged current datafile or control file Requires explicit invocation Operates as follows: Files are restored from backups Redo data is applied to the restored files from archived redo log files and online redo logs Media Recovery Media recovery is used to recover a lost or damaged current datafile or control file. You can also use it to recover changes that were lost when a datafile went offline without the OFFLINE NORMAL option. Restoring Files When you restore a file, you are replacing a missing or damaged file with a backup copy. Recovery of Files When you recover a file, changes recorded in the redo log files are applied to the restored files. Recovery Steps Restored datafiles Database containing committed and uncommitted transactions Recovered database Redo applied Undo applied 5 4 3 2 1 Datafile 1 Datafile 2 Datafile 3 Datafile 1 Datafile 2 Datafile 3 Datafile 1 Datafile 2 Datafile 3 Archived Redo log Online Redo log Recovery Steps 1. Damaged or missing files are restored from a backup. 2. Changes from the archived redo log files and online redo log files are applied as necessary. Undo blocks are generated at this time. This is referred to as rolling forward or cache recovery. 3. The database may now contain committed and uncommitted changes. 4. The undo blocks are used to roll back any uncommitted changes. This is known as rolling back or transaction recovery. 5. The database is now in a recovered state. Restoration and Datafile Media Recovery with User-Managed Procedures Restore files using operating system commands Recover files using the SQL*Plus RECOVER
