2 Getting Started with RMAN
New users can start with RMAN right away by understanding the most important RMAN concepts and learning how to perform backup and recovery tasks.
Note that the topics described in this chapter are not a substitute for the rest of the backup and recovery documentation set.
2.1 Overview of the RMAN Environment
Recovery Manager (RMAN) is an Oracle Database client that performs backup and recovery tasks on your databases and automates administration of your backup strategies. It greatly simplifies backing up, restoring, and recovering database files.
The RMAN environment consists of the utilities and databases that play a role in backing up your data. At a minimum, the environment for RMAN must include the following components:
-
An Oracle Database to which RMAN is connected with the
TARGET
keyword. A target database is a database on which RMAN is performing backup and recovery operations. RMAN always maintains metadata about its operations on a database in the control file of the database. The RMAN metadata is known as the RMAN repository. -
The RMAN client
An Oracle Database executable that interprets commands, directs server sessions to execute those commands, and records its activity in the target database control file. The RMAN executable is automatically installed with the database and is typically located in the same directory as the other database executables. For example, the RMAN client on Linux is located in
$ORACLE_HOME/bin
.
Some environments use the following optional components:
-
A disk location in which the database can store and manage files related to backup and recovery. You set the fast recovery area location and size with the
DB_RECOVERY_FILE_DEST
andDB_RECOVERY_FILE_DEST_SIZE
initialization parameters. -
An application required for RMAN to interact with sequential media devices such as tape libraries. A media manager controls these devices during backup and recovery, managing the loading, labeling, and unloading of media. Media management devices are sometimes called SBT (system backup to tape) devices.
-
A separate database schema used to record RMAN activity against one or more target databases. A recovery catalog preserves RMAN repository metadata if the control file is lost, making it much easier to restore and recover following the loss of the control file. The database may overwrite older records in the control file, but RMAN maintains records forever in the catalog unless the records are deleted by the user.
This chapter explains how to use RMAN in the most basic configuration, which is without a recovery catalog or media manager.
See Also:
-
Recovery Manager Architecture for a more detailed overview of the RMAN environment
-
Oracle Database Backup and Recovery Reference for
BACKUP
command syntax and semantics
2.2 Starting RMAN and Connecting to a Database: Quick Start
Before you perform any operations using RMAN, you must connect to a target database.
The RMAN client is started by issuing the rman
command at the command prompt of your operating system. RMAN displays a prompt for your commands as shown in the following example:
% rman RMAN>
RMAN connections to a database are specified and authenticated in the same way as SQL*Plus connections to a database. The only difference is that RMAN connections to a target or auxiliary database require either the SYSDBA
or SYSBACKUP
privilege. Any user can be granted this privilege.
Caution:
Good security practice requires that you not enter passwords in plain text on the command line. Enter passwords in RMAN only when requested by an RMAN prompt. See Oracle Database Security Guide to learn about password protection.
Note:
For RMAN operations, auditing is always enabled, by default, in the unified auditing mode. However, auditing is disabled if you using a mixed mode auditing environment. See Oracle Database Security Guide to learn more about auditing.You can connect to a database with command-line options or by using the CONNECT TARGET
command. The following example starts RMAN and then connects to a target database through Oracle Net as user sbu
, which is created with the SYSBACKUP
privilege. RMAN prompts for a password.
% rman
RMAN> CONNECT TARGET "sbu@prod AS SYSBACKUP"
target database Password: password
connected to target database: PROD (DBID=39525561)
When using the multitenant architecture, you can connect to the root or to a specified pluggable database (PDB) as described in "Making Database Connections with RMAN".
To quit the RMAN client, enter EXIT
at the RMAN prompt:
RMAN> EXIT
Syntax of Common RMAN Command-line Options
RMAN [ TARGET connectStringSpec | { CATALOG connectStringSpec } | LOG ['] filename ['] [ APPEND ] . . . ]... connectStringSpec::= ['] [userid] [/ [password]] [@net_service_name] [']
The following example appends the output from an RMAN session to a text file at
/tmp/msglog.log
% rman TARGET / LOG /tmp/msglog.log APPEND
See Also:
Starting and Interacting with the RMAN Client, to learn more about starting and using the RMAN client
About the SYSBACKUP
Administrative Privilege
When you install Oracle Database, the SYSBACKUP
user account is automatically created. The SYSBACKUP
user account provides the SYSBACKUP
administrative privilege to a designated user.
Oracle recommends that you create a user and grant the SYSBACKUP
administrative privilege to the user to perform Oracle Recovery Manager (RMAN) backup and recovery operations from RMAN or SQL*Plus. Do not use the default SYSBACKUP
user account for this purpose.
sbu
who is granted the SYSBACKUP
privilege:% rman
RMAN> CONNECT TARGET 'sbu@prod AS SYSBACKUP'
Note:
Starting with Oracle Database 23ai, theSYSBACKUP
administrative privilege has dictionary protection enabled for security reasons. To prevent improper use of system privileges, Oracle recommends that you retain the dictionary protection for the SYSBACKUP
user account. You can temporarily disable the dictionary protection, if necessary. See, Managing Dictionary Protection for Oracle-Maintained Schemas, in the Oracle Database Security Guide.
2.3 Showing the Default RMAN Configuration
The RMAN backup and recovery environment is preconfigured for each target database. The configuration is persistent and applies to all subsequent operations on this target database, even if you exit and restart RMAN.
RMAN configuration settings can specify backup devices, set up connections to those devices (known as channels), set policies affecting backup strategy, and more.
To show the current configuration for a database:
The output lists the CONFIGURE
commands to re-create this configuration.
See Also:
Configuring the RMAN Environment, and Configuring the RMAN Environment: Advanced Topics, to learn how to configure the RMAN environment
2.4 Backing Up a Database: Quick Start
Use the BACKUP command to back up files. RMAN backs up data to the configured default device for the type of backup requested.
By default, RMAN creates backups on disk. If a fast recovery area is enabled, and if you do not specify the FORMAT
parameter (see Table 2-1), then RMAN creates backups in the recovery area and automatically gives them unique names.
By default, RMAN creates backup sets rather than image copies. A backup set consists of one or more backup pieces, which are physical files written in a format that only RMAN can access. A multiplexed backup set contains the blocks from multiple input files. RMAN can write backup sets to disk or tape.
If you specify BACKUP
AS
COPY
, then RMAN copies each file as an image copy, which is a bit-for-bit copy of a database file created on disk. Image copies are identical to copies created with operating system commands like cp
on Linux or COPY
on Windows, but are recorded in the RMAN repository and so are usable by RMAN. You can use RMAN to make image copies while the database is open.
The following sections describe backing up databases in different modes:
See Also:
-
RMAN Backup Concepts, to learn concepts relating to RMAN backups
-
Backing Up the Database, to learn how to back up database files with RMAN
-
Oracle Database Backup and Recovery Reference for
BACKUP
command syntax and semantics
2.4.1 About Typical RMAN Backup Options
The BACKUP
command includes a host of options, parameters, and clauses that control backup output.
Table 2-1 lists some typical backup options.
Table 2-1 Common Backup Options
Option | Description | Example |
---|---|---|
|
Specifies a location and name for backup pieces and copies. You must use substitution variables to generate unique file names. The most common substitution variable is |
BACKUP FORMAT 'AL_%d/%t/%s/%p' ARCHIVELOG LIKE '%arc_dest%'; |
|
Specifies a user-defined string as a label for the backup. If you do not specify a tag, then RMAN assigns a default tag with the date and time. Tags are always stored in the RMAN repository in uppercase. |
BACKUP TAG 'weekly_full_db_bkup' DATABASE MAXSETSIZE 10M; |
See Also:
-
Oracle Database Backup and Recovery Reference for information about the format options
2.4.2 Backing Up a Database in ARCHIVELOG Mode
If a database runs in ARCHIVELOG
mode, then you can back up the database while it is open.
A backup is called an inconsistent backup if it contains changes after its checkpoint. If you have the archived redo logs needed to recover the backup, open database backups are as effective for data protection as consistent backups.
To back up the database and archived redo logs while the database is open:
2.4.3 Backing Up a Database in NOARCHIVELOG Mode
If a database runs in NOARCHIVELOG
mode, then the only valid database backup is a consistent backup.
For the backup to be consistent, the database must be mounted after a consistent shutdown. Recovery is not specifically required after restoring the backup, but you would lose any transactions made after the backup. You can recover with archived logs from a consistent backup to minimize data loss.
To make a consistent database backup:
2.4.4 Making Incremental Backups: Quick Start
Incremental backups capture block-level changes to a database made after a previous incremental backup.
If you specify BACKUP
INCREMENTAL
, then RMAN creates an incremental backup of a database. Incremental backups are generally smaller and faster to make than full database backups. Recovery with incremental backups is faster than using redo logs alone.
The starting point for an incremental backup strategy is a level 0 incremental backup, which backs up all blocks in the database. An incremental backup at level 0 is identical in content to a full backup, however, unlike a full backup the level 0 backup is considered a part of the incremental backup strategy.
A level 1 incremental backup contains only blocks changed after a previous incremental backup. If no level 0 backup exists in either the current or parent database incarnation when you run a level 1 backup, then RMAN makes a level 0 backup automatically.
Note:
You cannot make incremental backups when a NOARCHIVELOG
database is open, although you can make incremental backups when the database is mounted after a consistent shutdown.
A level 1 backup can be a cumulative incremental backup, which includes all blocks changed since the most recent level 0 backup, or a differential incremental backup, which includes only blocks changed since the most recent incremental backup. Incremental backups are differential by default.
During a restore operation, RMAN will first restore a level 0 backup, then automatically apply incremental backups and redo logs as needed. This will re-apply the changes that were made to the database since the start of the backup.
To make incremental backups of the database:
See Also:
"About RMAN Incremental Backups" for a more detailed conceptual overview of incremental backups and "Making and Updating RMAN Incremental Backups"
2.4.5 Making Incrementally Updated Backups
Incrementally updated backups enable you to implement an efficient incremental forever backup strategy.
The RMAN incrementally updated backup feature has the following main features:
-
The strategy requires a level 0 data file copy as a base. This copy has either a system-defined or user-defined tag.
-
Periodically, level 1 differential backups are created with the same tag as the level 0 data file copy. The
BACKUP FOR RECOVER OF COPY
command specifies that an incremental backup contains only blocks changed since the most recent incremental backup with the same tag. -
Periodically, the incremental backups are applied to the level 0 data file copy. Because the data file copy has been updated with more recent changes, it now requires less media recovery.
Table 2-2 explains which options to use with FOR RECOVER OF COPY
to implement an incrementally updated backup strategy.
Table 2-2 FOR RECOVER OF COPY Options
BACKUP Option | Description | Example |
---|---|---|
|
Use If no level 0 data file copy with the specified tag exists in either the current or parent database incarnation, then RMAN creates a level 0 data file copy with the specified tag. |
BACKUP INCREMENTAL LEVEL 1 FOR RECOVER OF COPY WITH TAG 'incr_update' DATABASE; |
|
Specifies where RMAN creates the data file copy if a copy does not exist. If you add a new data file to the database, then you do not need to change your script, because RMAN automatically creates the level 0 copy required by the incremental backup routine. |
BACKUP INCREMENTAL LEVEL 1 FOR RECOVER OF COPY DATAFILECOPY FORMAT '/disk2/df1.cpy' DATABASE; |
To implement an incrementally updated backup strategy:
-
Start RMAN and connect to a target database as described in "Starting RMAN and Connecting to a Database".
-
Run the
RECOVER COPY
andBACKUP INCREMENTAL
commands.The following script, run on a regular basis, is all that is required to implement a strategy based on incrementally updated backups.
RECOVER COPY OF DATABASE WITH TAG 'incr_update'; BACKUP INCREMENTAL LEVEL 1 FOR RECOVER OF COPY WITH TAG 'incr_update' DATABASE;
See Also:
2.4.6 Validating Database Files and Backups: Quick Start
RMAN validation checks a backup to determine whether it can be restored. Validation also checks for corrupt blocks and missing files.
Use the VALIDATE
command to confirm that all database files exist, are in their correct location, and are free of physical corruption. The CHECK LOGICAL
option also checks for logical block corruption.
To validate database files:
See Also:
-
Oracle Database Backup and Recovery Reference for
VALIDATE
command syntax and semantics
2.4.7 Scripting RMAN Operations
RMAN supports the use of command files to manage recurring tasks such as weekly backups.
A command file is a client-side text file containing RMAN commands, exactly as you enter them at the RMAN prompt. You can use any file extension.
Stored scripts are an alternative to command files that allow scripts to be available to any RMAN client that can connect to the target database and its recovery catalog.
To create and run a command file:
See Also:
-
"Using Command Files with RMAN" to learn more about command files
-
"Using Substitution Variables in Command Files" to learn how to use substitution variables in command files and pass parameters at run time
2.5 Reporting on RMAN Operations: Quick Start
RMAN can use the information stored in the RMAN repository to generate reports on backup activities.
Use the RMAN LIST
and REPORT
commands for reporting on backup operations. Use the SHOW ALL
command to display the current RMAN configuration. In addition, RMAN provides a comprehensive set of views for generating custom reports.
This section contains the following topics:
2.5.1 Listing Backups: Quick Start
The LIST
BACKUP
and LIST
COPY
commands display information about backups and data file copies listed in the repository.
For backups, you can control the format of LIST
output with the options in Table 2-3 and Table 2-4.
Table 2-3 LIST Options for Backups
Option | Example | Explanation |
---|---|---|
|
|
Organizes the output by backup set. This is the default mode of presentation. |
|
|
Lists the backups according to which file was backed up. |
|
|
Displays summary output. |
For both backups and copies you have additional options shown in Table 2-4.
Table 2-4 Additional LIST Options
Option | Example | Explanation |
---|---|---|
|
|
Lists backups that are recorded in the RMAN repository but that were not present at the expected location on disk or tape during the last |
|
|
Lists data file backups or copies that have status |
To list backups and copies:
-
Start RMAN and connect to a target database as described in "Starting RMAN and Connecting to a Database".
-
Run the
LIST
command at the RMAN prompt.You can display specific objects, as in the following examples:
LIST BACKUP OF DATABASE; LIST COPY OF DATAFILE 1, 2; LIST BACKUP OF ARCHIVELOG FROM SEQUENCE 10; LIST BACKUPSET OF DATAFILE 1;
See Also:
-
"Listing Backups and Recovery-Related Objects" to learn more about the
LIST
command -
Oracle Database Backup and Recovery Reference for
LIST
command syntax
2.5.2 Reporting on Database Files and Backups: Quick Start
The REPORT
command performs more complex reporting analysis than the LIST
command.
Table 2-5 displays some of the main options of the REPORT command.
Table 2-5 REPORT Options
Option | Example | Explanation |
---|---|---|
|
|
Shows which files need backing up under current retention policy. Use optional |
|
|
Lists backups that are obsolete under the configured backup retention policy. Use the optional |
|
|
Reports the tablespaces and data files in the database at the current time (default) or a different time. |
|
|
Lists all data files for which an unrecoverable operation has been performed against an object in the data file since the last backup of the data file. |
To generate reports of database files and backups:
-
Start RMAN and connect to a target database as described in "Starting RMAN and Connecting to a Database".
-
Run the
REPORT
command at the RMAN prompt.The following example reports backups that are obsolete according to the currently configured backup retention policy:
REPORT OBSOLETE;
The following example reports the data files and temp files in the database:
REPORT SCHEMA;
See Also:
"Reporting on Backups and Database Schema" to learn how to use the REPORT
command for RMAN reporting
2.6 Maintaining RMAN Backups
RMAN repository metadata is always stored in the control file of the target database. The RMAN maintenance commands use this metadata when managing backups.
This section contains the following topics:
2.6.1 Cross-checking Backups: Quick Start
Use the CROSSCHECK
command to synchronize the logical records of RMAN backups and copies with the files on storage media.
If a backup is on disk, then CROSSCHECK
determines whether the header of the file is valid. If a backup is on tape, then RMAN queries the RMAN repository for the names and locations of the backup pieces. It is a good idea to crosscheck backups and copies before deleting them.
To crosscheck all backups and copies on disk:
See Also:
"Crosschecking the RMAN Repository" to learn how to crosscheck RMAN backups
2.6.2 Deleting Obsolete Backups: Quick Start
The DELETE command removes RMAN backups and copies from disk and tape, updates the status of the files to DELETED
in the control file repository, and removes the records from the recovery catalog (if you use a catalog).
If you run RMAN interactively, and if you do not specify the NOPROMPT
option, then DELETE
displays a list of files and prompts for confirmation before deleting any file in the list. The DELETE OBSOLETE
command is particular useful because RMAN deletes backups and data file copies recorded in the RMAN repository that are obsolete, that is, no longer needed. You can use options on the DELETE
command to specify what is obsolete or use the configured backup retention policy.
To delete obsolete backups and copies:
See Also:
"Deleting RMAN Backups and Archived Redo Logs" to learn how to use the DELETE
command
2.7 Rewinding a Database with Flashback Database: Quick Start
You can use the Oracle Flashback Database to rewind the whole database to a past time. Unlike media recovery, you do not need to restore data files to return the database to a past state.
To use the RMAN FLASHBACK DATABASE
command, your database must have been previously configured to generate flashback logs. This configuration task is described in "About Flashback Database". Flashback Database works by rewinding changes to the data files that exist at the moment that you run the command. You cannot use the flashback database to repair media failures or missing data files.
The database must be mounted when you issue FLASHBACK DATABASE
. You can flashback to any time within the flashback database window. If you have previously created a restore point, that is a convenience, but not required.
To rewind a database with Flashback Database:
See Also:
2.8 Restoring and Recovering Database Files: Quick Start
Use the RESTORE
and RECOVER
commands for RMAN restore and recovery of physical database files.
Restoring data files is retrieving them from backups as needed for a recovery operation. Media recovery is the application of changes from redo logs and incremental backups to a restored data file to bring the data file forward to a desired SCN or point in time.
This section contains the following topics:
See Also:
2.8.1 Preparing to Restore and Recover Database Files: Quick Start
To recover the database because a media failure damages database files, then first ensure that you have the necessary backups.
You can use the RESTORE ... PREVIEW
command to report, but not restore, the backups that RMAN can use to restore to the specified time. RMAN queries the metadata and does not actually read the backup files. The database can be open when you run this command.
To preview a database restore and recovery:
2.8.2 Recovering the Whole Database: Quick Start
Use the RESTORE
DATABASE
and RECOVER
DATABASE
commands to recover the whole database.
You must have previously made backups of all needed files. This scenario assumes that you can restore all data files to their original locations. If the original locations are inaccessible, then use the SET NEWNAME
command as described in "About Restoring Data Files to a Nondefault Location".
To recover the whole database:
2.8.3 Recovering Tablespaces: Quick Start
Use the RESTORE
TABLESPACE
and RECOVER
TABLESPACE
commands on individual tablespaces when the database is open. In this case, you must take the tablespace that needs recovery offline, restore and then recover the tablespace, and bring the recovered tablespace online.
If you cannot restore a data file to its original location, then use the RMAN
SET NEWNAME
command within a RUN
block to specify the
new file name and location. Afterward, use a SWITCH DATAFILE ALL
command to
update the control file to reflect the new names for all data files for which a SET
NEWNAME
has been issued in the RUN
command.
Unlike user-managed media recovery, you do not place an online tablespace in backup mode. RMAN does not require extra logging or backup mode because it knows the format of data blocks.
To recover an individual tablespace when the database is open:
You can also use RESTORE DATAFILE
and RECOVER DATAFILE
for recovery at the data file level.
2.8.4 Recovering Individual Data Blocks: Quick Start
RMAN can recover individual corrupted data file blocks.
When RMAN performs a complete scan of a file for a backup, any corrupted blocks are listed in V$DATABASE_BLOCK_CORRUPTION
. Corruption is usually reported in alert logs, trace files, or results of SQL queries.
To recover data blocks:
See Also: