怎样深入解析RMAN 备份与恢复

RMAN is a tool provided by Oracle for backing up and restoring databases. It can be used to take hot or cold backups of an entire database or individual tablespaces, and can also be used to perform point-in-time recovery. In this article, we will take a look at how to use RMAN to perform a hot backup of an entire database. To perform a hot backup with RMAN, we need to have the database in ARCHIVELOG mode. This means that all changes to the database are recorded in the online redo logs, which can then be used to recover the database to a specific point in time if necessary. If the database is not in ARCHIVELOG mode, then it can only be recovered to the time of the last backup. The first thing we need to do is connect to the database as the SYSDBA user: rman target / Once connected, we need to configure RMAN to use a channel to perform the backup. A channel is essentially a stream of data that RMAN uses to perform the backup. We can use as many channels as we like, but for this example we will just use one: configure channel device type disk format '/u01/backups/%U'; The format parameter specifies the location and name of the backup files that RMAN will create. The %U parameter will be replaced with a unique identifier for each backup file. Now that we have configured a channel, we can start the backup: backup database plus archivelog; This will start the backup of the database and all of the archived redo logs. The backup will continue until it is finished, at which point RMAN will disconnect from the database. Once the backup is complete, we can check the status of the backup by running the following command: report need backup; This will show us any files that need to be backed up in order to recover the database. In most cases, we will want to backup all of the files in order to have a complete recovery. If we need to recover the database to a specific point in time, we can use the following command: recover database until time 'YYYY-MM-DD HH24:MI:SS'; This will recover the database up to the specified time. Once the recovery is complete, we can open the database with the following command: alter database open; Now that the database is open, we can query it and use it as usual.