Retention policy of RMAN backup

What is the retention policy for backup (retention policy)

　　 Retention policy refers to whether a backup should be retained and for how long . have access to configure retention policy Command to create a consistent 、 Automatic backup retention policy . When a backup strategy takes effect ,rman Think of data files 、 The backup of control files is obsolete Of , That is to say, according to user configuration , These backups are no longer needed for recovery . Users can use report obsolete Order to find out obsolete And use delete obsolete Delete them .

　　 As the number of backups increases , Old backup files will become obsolete.rman Can identify obsolete The file of , But they will not be deleted automatically . You need to manually execute delete obsolete Delete them .

　　 If the database is configured with a fast flashback area , The database will flash back the disk according to the fast quota Rules automatically delete files in the flashback area . Flashback zone quota Rule with rman Backup policy rules are different , But the flashback area will not delete backup files that do not exceed the backup policy .

obsolete and expired It's two different concepts

　　 Whether the backup obsolete, It is determined by the backup strategy , It refers to exceeding the limit of the backup policy , Files that are no longer needed during recovery ;expired Refer to rman In execution crosscheck During the inspection , These files could not be found . In a word ,obsolete Refer to " No longer need ",expired Refer to " Can't find ".

　　 Retention policies are for data files and control files full Back up or level 0 Backup ( Whether it's datafile image copy, a proxy copy, or part of a backup set). about datafile copies and proxy copies, If rman You can delete it if you think it is no longer needed . For backup set datafile Backup , Only the entire backup set becomes obsolete Before it can be deleted .

　　 The backup strategy is not only for data files and control files full and level 0 The backup is valid , It also affects archived logs and level 1 Incremental backup . First rman Detect those data files 、 The control file backup is obsolete Of , then rman Archive logs that are no longer needed during recovery 、level 1 Incremental backup is considered obsolete Of .

report obsolete and delete obsolete How commands work ：

It is mainly divided into two steps

(1) First , about full backup、datafile copy and level 0 Incremental backup of ,rman Will be based on retention policy Identify which are obsolete Of .

(2) then , For archive logs and level 1 Incremental backup of , If it corresponds to full backup、datafile copy and level 0 Incremental backup of has been obsolete Of , It would also be considered obsolete Of , Because they are no longer needed for data recovery .

NOTE:  A 'delete obsolete' does not check that the archivelog files have been backed up before it deletes them. 

Types of retention backup policies ：( There are two types of backup )

(1)redundancy( redundancy )： Redundancy by default

1	​​rman> configure retention policy ​​​​to​​​ ​​redundancy x;​​

(2)recovery window( Restore window ) 

1	​​rman> configure retention policy ​​​​to​​​ ​​recovery window ​​​​of​​​ ​​x days;​​

When configuring the recovery window , The time should not be greater than the parameter control_file_record_keep_time Value .

Cancel the backup policy ：( Never set backup to obsolete)

1	​​rman> configure retention policy ​​​​to​​​ ​​none;​​

How to make backup unaffected by backup strategy :

Users may need to keep data backup for a long time ( beyond rman Retention policy settings ). This backup information should be recorded in rman repository in , But it should exceed rman Limitations of backup retention policies , Otherwise it will be marked as obsolete Of .

Can be used during backup keep keyword 、 Or use after backup change...keep To achieve .

For archive logs, you can use logs keyword , This will not be identified as obsolete Of

Example ：

1 2 3 4 5 6 7 8

​​# creates a backup ​​​​and​​​ ​​exempts it ​​​​from​​​ ​​retention policy until ​​​​last​​​ ​​day​​​ ​​of​​​ ​​2007​​ ​​rman> backup ​​​​database​​​ ​​keep until ​​​​time​​​ ​​"to_date('31-dec-2007', 'dd-mon-yyyy')"​​​ ​​nologs;​​ ​​# specifies that backupset 2 ​​​​is​​​ ​​no​​​ ​​longer exempt ​​​​from​​​ ​​the retention policy​​ ​​rman> change backupset 2 nokeep;​​ ​​# creates a backup that ​​​​is​​​ ​​indefinitely exempt ​​​​from​​​ ​​the retention policy​​ ​​rman> backup tablespace users keep forever nologs;​​