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.At least one allocate channel command must precede the recover commandunless it is known that no archivelog or incremental datafile backup sets willneed restoration.Furthermore, the appropriate type of device(s) must beallocated for the backup sets that will need restoration.If the appropriate typeof device is not available, then the recover command will fail.The restores ofdatafile incremental backup sets are performed in parallel if multiple channelsare allocated, with the degree of parallelism controlled by the number ofallocate channel commands.Database Point-In-Time RecoveryAn easy way of specifying the time to is to use set until.This command affectsany subsequent restore, switch and recover commands in the same runcommand.If a set until command is specified after a restore and before arecover, you may not be able to recover the database to the point in timerequired, as the files restored may already have timestamps more recent thanthat time; for this reason, the set until command is usually specified before therestore or switch command.set until This specifies a point in time for a subsequent restoreor recover command.The point in time may bespecified in one of the following ways:The set until command takes the following keywords:" time string" logseq integer thread integer" scn integerIf the time keyword is specified then string must be a formatted according tothe NLS date format specification currently in effect.This format is specifiedby the NLS_DATE_FORMAT environment variable on most platforms.8-36 Oracle8 Backup and Recovery Guide Recovery CommandsThere are three forms of Recovery Manager recover commands:" recover database" recover tablespace" recover datafileFor datafile and tablespace recovery, the target database must be started andmounted.If it is open, then the datafile(s) or tablespace(s) to be recovered mustbe offline.For database recovery, the database must be started but not open.If possible,the target database should be mounted.If the target database is not mounted,then Recovery Manager uses the values of the db_name and db_domaininit.ora parameters to determine which target database it is operating against.If the db_name parameter is not specified in the target database init.ora file,then the recover command will fail.If there are multiple target databases withthe same name and domain in the recovery catalog, again, the recovercommand will fail.Datafile RecoveryPerform this form of recovery when a media failure has damaged one or moredatafiles.Tablespace RecoveryPerform this form of recovery when a media failure has damaged all datafilesfor a tablespace, or when a tablespace is to be recovered to a previous point-in-time.Performing tablespace recovery is also an easy way of naming the files that areto be recovered.Any files not requiring recovery are simply ignored.Database RecoveryPerform database recovery under the following circumstances:" media failure has damaged the entire database" the entire database is to be recovered to a previous point-in-time" media failure has damaged the control file" create controlfile has been executedPerforming Backup and Recovery with Recovery Manager 8-37 Recover Command Object Listdatafile This specifies a list of one or more datafiles torecover.Datafiles may be specified by filename or byfilenumber.The name must be the current name ofthe datafile as known in the recovery catalog.If thedatafile has been renamed in the control file since thelast time it was backed up or the last time a resynccatalog was done, then the old name of the datafilemust be used.tablespace This specifies a list of one or more tablespaces torecover.database This specifies that the entire database is to berecovered.You can specify an optional until_clausethat causes the recovery to stop when the specifieduntil condition has been reached.An optional skip_clause may also be specified.Theskip_clause lists tablespaces that should not berecovered
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