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在Oracle 12.2之前，当需要恢复数据库到某个时间点的时候，需要确定SCN，或者日志序列号，或者一个时间点，以便尽可能多的应用归档日志，进而尽可能多的恢复数据。从12.2开始，RMAN新增参数“UNTIL AVALIABLE REDO”，语法如下:

RMAN将会根据控制文件信息和归档日志、线日志、归档日志备份集的物理可用性，将数据库恢复到最后一个可用的归档日志。所以在进行恢复的时候，可以不需要指定SCN，或者时间或者日志序列号。需要注意的是，数据文件仍然需要在一致的情况下，数据库才能打开。

需要注意的是，这些新特性有如下的限制条件：

l  不能针对恢复数据文件或者表空间使用这个命令。

l  不能针对恢复PDB使用这个命令。

l  只能针对全库恢复使用这个命令。

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In this Document

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APPLIES TO:

Oracle Database - Enterprise Edition - Version 12.2.0.1 to 12.2.0.1 [Release 12.2]
Information in this document applies to any platform.

GOAL

 Goal of this Document is to explain how to use the New Feature in 12.2  Recover database until available redo.

 The New Syntax available in 12.2 is

  

  

Finds the last available archived redo log and online redo logs, and recovers the database to the point where a log is missing.

The database files still needs to be consistent enough to open the database.

LIMITATIONS/RESTRICTIONS

 

1. You cannot recover a Datafile or Tablepace with this command.
2. You cannot recover PDB using this command.
3. You can use this command only while performing recovery of whole database.

SOLUTION

Whenever a database needs to be restored to a Point in time we  need to determine  SCN, or the Sequence or time  in order to apply as many archived logs as possible, to recover as much data as possible.

The new syntax helps reduce this work as rman would physically check for the available Archive/redo copy or backupset and do the recovery till the last available Archivelog based on information in Controlfile and physical availability of the Archivelog copy/redo log/Archive log backupsets.So you don't have to specify any until SCN ,Sequence or time.

Here is an example which explains the new feature.

In this example we will delete couple of Archivelog's after the backups are taken.

A> Using Current Controlfile.

Step1 :- Take a backup of the database

 

 

So the last archivelog backed up is sequence 10 and thats the Minimum archivelog till which recovery needs to be done to open the database after restore.  

 

Step 2 :-  Do couple of Log switch and delete Couple of Archivelogs 

  

 

Step 3 : Restore the database from backup taken in Step 1

  

  

 

Step 4:- Use the new syntax

  

 

 

B> When using backup or restored controlfile.

The only change is Once the controlfile is restored and database is mounted ensure you Catalog all the backuppieces that are required so restored controlfile is aware about the backuppiece's.

You can use Catalog start with  or Catalog backuppiece '<path and name>' command.

The steps to restore  database and recovery are same as Step A.