Backup Retention Policy in Font

Printer QR in Font Backup Retention Policy

A backup retention policy tells RMAN when to consider backups of data files and log files obsolete. Note that that when you tell RMAN to consider a backup file obsolete after a certain time period, RMAN only marks the file obsolete it doesn t delete it. You must go in and delete the obsolete files. You can set a retention policy by using either of two methods: the default REDUNDANCY option or the RETENTION WINDOW option. In both cases, you use the CONFIGURE RETENTION POLICY command to set the retention policy for all of your database files by default.

The REDUNDANCY option lets you specify how many copies of the backups you want to retain. The default is 1. You set the retention policy this way: RMAN> CONFIGURE RETENTION POLICY TO REDUNDANCY 2; new RMAN configuration parameters: CONFIGURE RETENTION POLICY TO REDUNDANCY 2; new RMAN configuration parameters are successfully stored starting full resync of recovery catalog full resync complete RMAN> Let s say you re backing up your data files every day. The previous RMAN command specifies that RMAN keep only two backups of each database files. RMAN will also retain all redo logs required to recover the two days worth of data file backups. Any backups that are older than two days are considered obsolete. Of course, you can save to tape and archive a much older set of backups. Archived backups are useful if you ever want to perform a PITR to a time further back than your recent backup. In addition, if your current backups end up being unusable, you have an alternative set of backups available.

Setting the backup retention policy using the RECOVERY WINDOW option enables you to specify how far back in time you want to recover from when your database is affected by a media failure. RMAN will keep all backups of data files and log files one backup older than the recovery window. For example, if the recovery window is seven days, RMAN will save all backups starting from the backups done immediately before the seven-day period. You set the recovery window as follows: RMAN> CONFIGURE RETENTION POLICY TO RECOVERY WINDOW OF 14 DAYS; old RMAN configuration parameters: CONFIGURE RETENTION POLICY TO REDUNDANCY 2; new RMAN configuration parameters: CONFIGURE RETENTION POLICY TO RECOVERY WINDOW OF 14 DAYS; new RMAN configuration parameters are successfully stored starting full resync of recovery catalog full resync complete RMAN> As you can see in this example, you can set the redundancy number or a recovery window, but not both. A change in the value of either of the two options will supersede the values of the existing option.

The default device for backups is disk; that is, RMAN will automatically make backups to a file system on your server. If you want to back up to tape, you configure the default device type to sbt (all tape destinations are referred to as sbt). Here s an example: RMAN> CONFIGURE DEFAULT DEVICE TYPE TO sbt; old RMAN configuration parameters: CONFIGURE DEFAULT DEVICE TYPE TO DISK; new RMAN configuration parameters: CONFIGURE DEFAULT DEVICE TYPE TO 'SBT_TAPE'; new RMAN configuration parameters are successfully stored starting full resync of recovery catalog full resync complete RMAN> If you wish to switch the default device back to disk, you can do so with the following command: RMAN> CONFIGURE DEFAULT DEVICE TYPE TO DISK; old RMAN configuration parameters: CONFIGURE DEFAULT DEVICE TYPE TO 'SBT_TAPE'; new RMAN configuration parameters: CONFIGURE DEFAULT DEVICE TYPE TO DISK; new RMAN configuration parameters are successfully stored starting full resync of recovery catalog full resync complete RMAN>

Channels are the means by which RMAN conducts its backup and recovery operations, and they represent a single stream of data to a particular device (such as a tape). If you have four channels configured, four connections will be made to the target database to open four separate server sessions.