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.Warning: After opening the database with the RESETLOGS option, existingbackups cannot be used for subsequent recovery beyond the time when thelogs were reset.You should therefore shutdown the database and make aconsistent whole database backup.Doing so will enable recovery of databasechanges subsequent to using the RESETLOGS option.Database Backups After Using the RESETLOGS OptionOnce you have opened a database with the RESETLOGS option, Oraclerecommends you immediately perform a whole database backup.If this is notdone, and a further disaster occurs, requiring a restore of all or part of yourdatabase, you will lose all work performed since opening the database.Note: There is one exception to this rule.See Recovery After Using theRESETLOGS Option on page 3-9 for details.When a database is opened with the RESETLOGS option, Oracleautomatically:" creates a new incarnation of the database" resets the log sequence number to 13-4 Oracle8 Backup and Recovery Guide " reformats the online redo log files if they exist (otherwise they arecreated)The reason Oracle performs these three actions is to be able to identify whicharchived redo logs apply to which incarnations of the database.Backup options in NOARCHIVELOG modeIf you are in NOARCHIVELOG mode, your only option is to make a coldconsistent whole database backup.Backup options in ARCHIVELOG modeIf you are in ARCHIVELOG mode, you can either perform a consistent (thatis, closed) whole database backup, or an inconsistent (that is, open) databasebackup.The option you choose depends on:" the time available before the database absolutely must be available" the importance of data entered after opening the database with theRESETLOGS optionIf your most important criteria is getting the database up and available, youronly option is to perform open-database backups.The risk involved in performing an open backup is that if the backups do notcomplete before you have another media failure, you lose all changes madesince opening the database with the RESETLOGS option, as you cannot use abackup taken before opening the database with that option to recover thisincarnation of the database.Note: There is one and only one exception to this.See Recovery After Usingthe RESETLOGS Option on page 3-9If the most important criteria is to be able to restore in case of another failure,then it may be more prudent to take a consistent (closed) database backup.If time permits, Oracle recommends a consistent whole database backup.Export Database Data for Added Protection and FlexibilityBecause the Oracle Export utility can selectively export specific objects, youmight consider exporting portions or all of a database for supplementalprotection and flexibility in a database s backup strategy.Database exports arenot a substitute for whole database backups and cannot provide the samecomplete recovery advantages that the built-in functionality of Oracle offers.When to Perform Backups 3-5 See Also: For more information on the Export utility, see the Oracle8 ServerUtilities guide.Consider Distributed Database BackupsIf a database is a node in a distributed database, consider the followingguidelines:" All databases in the distributed database system should be operated inthe same archiving mode." If the databases in a distributed database system are operating inARCHIVELOG mode, backups at each node can be performedautonomously (individually, without time coordination)." If the databases in a distributed database system are operating inNOARCHIVELOG mode, consistent whole database backups must beperformed at the same (global) time, to plan for global distributeddatabase recovery.For example, if a database in New York is backed upat midnight EST, the database in San Francisco should be backed up at9 PM PST.Test Backup and Recovery StrategiesTest your backup and recovery strategies in a test environment before andafter you move to a production system
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