4-User Managed Complete Recovery

4-User Managed Complete Recovery - User Managed Complete...

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1 User Managed Complete Recovery Presenter Tathagata Bhattacharjee
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User Managed Complete Recovery Tathagata Bhattacharjee 2 Objectives ± After completing this lesson you should be able to do the following ± Describe media recovery ± Perform recovery in NOARCHIVELOG mode ± Restore datafiles to different locations ± Relocate and recover a tablespace by using archived redo log files ± Describe read-only tablespace recovery
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User Managed Complete Recovery Tathagata Bhattacharjee 3 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
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User Managed Complete Recovery Tathagata Bhattacharjee 4 ± 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 file are applied to the restored files
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User Managed Complete Recovery Tathagata Bhattacharjee 5 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 data may now contain committed and uncommitted changes
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User Managed Complete Recovery Tathagata Bhattacharjee 6 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
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User Managed Complete Recovery Tathagata Bhattacharjee 7 Restoration and Datafile Media Recovery with User-Managed Procedures ± Restore files using OS commands ± Recover files using the SQL*Plus RECOVER command
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User Managed Complete Recovery Tathagata Bhattacharjee 8 ± When you restore a file, you use OS commands to copy the file from a backup ± You can restore datafiles, control files, archived redo log files and the parameter file ± You use the SQL*Plus RECOVER command to apply redo log files to the restored files. ± You can perform automatic recovery or steps through the log files to apply the changes
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User Managed Complete Recovery Tathagata Bhattacharjee 9 ARCHIVELOG and NOARCHIVELOG Modes ± The archiving mode you choose for your database affects your options for recovery if you have a media failure ± The following factors should be considered in setting the archive log mode
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User Managed Complete Recovery Tathagata Bhattacharjee 10 ± NOARCHIVELOG mode may be suitable when: ± Data loss between backups can be tolerated (training and development) ± It is faster to reapply transactions (from batch files) ± Data rarely changes (non-OLTP)
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User Managed Complete Recovery Tathagata Bhattacharjee 11 ± ARCHIVELOG mode is preferable when ± The database cannot be shutdown for a closed backup ± Data loss cannot be tolerated ± It is easier to recover using archived redo log files than reapplying transactions (OLTP)
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4-User Managed Complete Recovery - User Managed Complete...

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