Subject: | Creating a Disk only backup script to achieve a recovery window using oracle recommended strategy in flash recovery area | |||
Note:280709.1 | Type: | BULLETIN | ||
Last Revision Date: | 21-SEP-2004 | Status: | PUBLISHED | |
***This article is being delivered in Draft form and may containerrors. Please use the MetaLink "Feedback" button to adviseOracle of any issues related to this article.*** PURPOSE------- To understand and using oracle recommended strategy for disk only backupsto achieve a recovery window of N days. This note is essentially written to clarify bug# 3826979. SCOPE & APPLICATION-------------------All users of RMAN that have the need of backing up the database to disk only and may use flash recovery area. Topics discussed---------------- 1. Disk backup strategy2. How to obtain recovery window of N days using disk backup strategy?. 1.Disk Backup Strategy----------------------Oracle recommended disk backup strategy is to have a) retention policy is redundancy 1 b) create a copy of database on disk in flash recovery area c) take cumulative incrementals over this copy d) rollforward the copy of database daily a) RMAN> CONFIGURE RETENTION POLICY TO REDUNDANCY 1; b, c & d) The backup script is like run { recover copy of database with tag ORA_BACKUP; backup device type disk incremental level 1 for recover of copy database with TAG ORA_BACKUP; } The first command roll forwards the copy of database with tag ORA_BACKUP to latest point in time by applying incrementals over the backup. The second command creates an incremental backup with parent as copy of database with tag ORA_BACKUP. If there is no copy of database with tag ORA_BACKUP, then it will create a copy. Timeline first command second command ======== ============= ============== Day 1 no copy of rollforward creates a copy of database Day 2 no incr to be applied creates incremental Day 3 copy roll forwarded through Day2 creates incremental Day 4 copy roll forwarded through Day3 creates incremental ... As you can see that the above script will make the copy one day older at given time. Hence, the script is good to attain a recovery window of 1 days assuming the script is executed every night. 2. How to obtain recovery window of N days using disk backup strategy?.----------------------------------------------------------------------- Now instead of attaining 1 day recovery window on disk, user may wish to achieve a recovery window of N days. For example, assume user want a recovery window of 15 days. There are two changes that needed to be done - a) change retention policy to recovery window of 15 days; b) change backup script to keep copy 15 days older a) RMAN> configure retention policy to recovery window of 15 days; This configuration is optional. We can obtain recovery window of 15 days with redundancy 1 and using below script. The advantage of changing the configuration is to make sure that RMAN doesn't mark any tape backups (if any) as obsolete that are require to attain 15 day recovery window. b) The backup script is like run { recover copy of database with tag ORA_BACKUP until time 'sysdate - 16'; backup device type disk incremental level 1 for recover of copy database with TAG ORA_BACKUP; } We use one day more as 'sysdate-16' to take care of daylight savings. The first command roll forwards the copy of database with tag ORA_BACKUP to a point in time 16 days older by applying incrementals over the backup. The second command creates an incremental backup with parent as copy of database with tag ORA_BACKUP. If there is no copy of database with tag ORA_BACKUP, then it will create a copy. Timeline first command second command ======== ============= ============== Day 1 no copy of rollforward creates a copy of database Day 2 no incr to applied creates incremental ... Day 15 no incr to applied creates incremental Day 16 copy roll forwarded through Day2 creates incremental Day 17 copy roll forwarded through Day3 creates incremental ... As you can see you can achieve a recovery window of 15 days on disk.
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