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.If a datafile exists in the data dictionary but not in the new control file, Oraclecreates a placeholder entry in the control file under MISSINGnnnn (wherennnn is the file number in decimal).MISSINGnnnn is flagged in the control fileas being offline and requiring media recovery.The actual datafilecorresponding to MISSINGnnnn can be made accessible by renamingMISSINGnnnn, so that it points to the datafile only when the datafile was read-only or offline normal.If, on the other hand, MISSINGnnnn corresponds to adatafile that was not read-only or offline normal, then the rename operationcannot be used to make the datafile accessible, because the datafile requiresmedia recovery that is precluded by the results of RESETLOGS.In this case,the tablespace containing the datafile must be dropped.In contrast, if a datafile indicated in the control file is not present in the datadictionary, Oracle removes references to it from the new control file.In bothcases, Oracle includes an explanatory message in the ALERT file to let youknow what was found.See Also: For more information see the Oracle8 Server Administrator s Guide.For more information about applying redo logs, see Applying Redo LogFiles on page 11-4.Recovering a Database 11-29 Performing Change-based RecoveryThis section describes how to perform change-based recovery.To Perform Change-based Recovery1.If the database is still open and incomplete media recovery is necessary,shut down the database using the Enterprise Manager Shutdown Abortmode of the Shutdown Database dialog box, or the SHUTDOWNcommand with the ABORT option.2.Make a whole backup of the database (all datafiles, a control file, and theparameter files of the database) as a precautionary measure, in case anerror is made during the recovery procedure.3.If a media failure occurred, correct the hardware problem that causedthe media failure.4.If the current control files do not match the physical structure of thedatabase at the intended time of recovery (for example, if a datafile wasadded after the point in time to which you intend to recover), thenrestore a backup of the control file that reflects the database s physicalfile structure (contains the names of datafiles and online redo log files)at the point at which incomplete media recovery is intended to finish.Review the list of files that correspond to the current control file as wellas each control file backup to determine the correct control file to use.Ifnecessary, replace all current control files of the database with thecorrect control file backup.You can, alternatively, create a new controlfile to replace the missing one.Note: If a database control file cannot function or be replaced with acontrol file backup, you must edit the parameter file associated with thedatabase to modify the CONTROL_FILES parameter.5.Restore backup files of all the datafiles of the database.All backup filesused to replace existing datafiles must have been taken before theintended time of recovery.For example, if you intend to recover to redolog sequence number 38, then restore all datafiles with backupscompleted before redo log sequence number 38.If you do not have a backup of a specific datafile, you can create anempty replacement file, which can be recovered.If a datafile was added after the intended time of recovery, it is notnecessary to restore a backup for this file, as it will no longer be used forthe database after recovery is complete.If the hardware problem that caused a media failure has been solvedand all datafiles can be restored to their original locations, do so, and11-30 Oracle8 Backup and Recovery Guide skip Step 8 of this procedure.If a hardware problem persists, restoredamaged datafiles to an alternative storage device.Note: Files in read-only tablespaces should be offline if you are using a controlfile backup.Otherwise, recovery will try to update the headers of the read-only files.6
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