11g, 12c, Administration, backup/recovery, RMAN

Oracle 12c – Recovery Manager (RMAN) Utility Commands

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RMAN is the preferred method used for backup and recovery of Oracle database.   This article gives a brief overview of commands used to Configure, Display Configurations, Reset to Default, and take simple backups.

 

 

 

  • The SHOW command gives current settings for RMAN utility to the associate target database.
  • The CLEAR command resets to RMAN defaults.
  • The following command allows for three backup copies of all data files and control files. the forth oldest will be considered obsolete and deleted. default is 1.
    • RMAN> configure retention policy to redundancy 3;
  • The following ensures that backup window of recovery is at least 7 days in the past, backups will be kept to allow for this regardless of redundancy policy.
    • RMAN> configure retention policy to recovery window of 7 days;
  • The following changes the default device type to tape, the default is disk.
    • RMAN> configure default device type to sbt;
  • Regardless of default device type, you can perform backup to specific backup with ‘device type’ clause.
    • RMAN> backup device type sbt database;
    • RMAN> backup device type disk database;
  • RMAN can backup as an image copy or backup set.
    • RMAN> configure device type disk backup type to backupset;
    • RMAN> configure device type disk backup type to copy;
  • TAPE backups can only be backup sets.
  • binary compression can be used with backupsets with COMPRESSED option.
    • RMAN> configure device type disk backup type to compressed backupset;
    • RMAN> configure device type sbt backup type to compressed backupset;
  • An RMAN channel is a connection to db server process, use the configure channel command to create and change channel settings.
    • RMAN> configure channel device type disk maxpiecesize 1g;
    • RMAN> configure channel device type disk format /tmp/%U;
  • By default RMAN allocates a single disk channel for all operations, you can specify a distinct file name for a channel, but RMAN does not create a backup in the fast recovery area.
    • RMAN> configure channel device type disk format ‘/u01/oradata/orcl_df%t_s%s_s%p’;
    • RMAN> configure channel device type disk format ‘+dgroup1’;
  • You can perform parallel backups by defining multiple channels for use.
    • RMAN> RUN
    • {
    • allocate channel u01 device type disk format ‘/u01/%u’;
    • allocate channel u02 device type disk format ‘/u02/%u’;
    • backup database plus archivelog;
    • }
  • RMAN can be configured to autobackup control files and if in archivelog mode and a change occurs to controlfiles, they will be automatically backed up.
    • RMAN> configure controlfile autobackup on;
    • RMAN> configure controlfile autobackup off;
  • RMAN configuration can be reset to default values by using the CLEAR option.
    • RMAN> configure default device type clear;
    • RMAN> configure retention policy clear;
    • RMAN> configure controlfile autobackup clear;
  • When RMAN optimization is enabled, it will skip files that have not changed since the last backup set. RMAN determines this by:
    • Datafile must have same DBID, checkpoint SCN, creation SCN, resetlogs scn and time as one already in backup set.
    • Datafile must be offline, read-only or closed.
    • Archived log – must have same DBID, thread, sequence number, resetlogs scn and time.
    • Backup Set – must have the same DBID, backup set record id, and stamp.
  • RMAN will still take a backup of retention policy requires and if TO DESTINATION is used with BACKUP RECOVERY AREA or BACKUP RECOVERY FILES.
  • Turn RMAN optimization on and off with:
    • RMAN> configure backup optimization on;
  • Once optimization is enabled, backup will not be performed, if nothing has changed since the last valid backup.
  • Backup optimization can be overridden by the FORCE option.
    • RMAN> backup database force;
    • RMAN> backup archivelog all force;

 

 

 

Larry Catt

OCP

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