Database in ARCHIVELOG Mode

• For RMAN to back up the database while it is running, the database must be in ARCHIVELOG mode. This mode allows the database to archive redo logs, which RMAN uses for recovery.

To check if the database is in ARCHIVELOG mode:
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SQL> SELECT LOG_MODE FROM V$DATABASE;

OR

SQL> ARCHIVE LOG LIST; 

To enable ARCHIVELOG mode (requires database restart):
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SHUTDOWN IMMEDIATE;

STARTUP MOUNT;

ALTER DATABASE ARCHIVELOG;

ALTER DATABASE OPEN;

2. Sufficient Disk Space

• Ensure there is enough disk space available for backups. This includes space for the RMAN backupsets and archived redo logs.

In RMAN, you can use the SHOW ALL command to display the current configuration settings for RMAN parameters. This command provides an overview of all RMAN configuration settings, including retention policies, backup destinations, compression, encryption, and other important options.

Here's how to display the current configuration for all RMAN parameters:

RMAN SHOW ALL Command

• This command lists all RMAN configuration settings, including their default or modified values.

Command:
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RMAN> SHOW ALL;

The output will show settings such as:

• Retention Policy

• Backup Optimization

• Backup Device Type

• Control File Autobackup

• Encryption Algorithm

• Snapshot Control File Location

• Channel configurations

2. Details of Key RMAN Parameters

Here’s a breakdown of important RMAN parameters and what they control:

a. Retention Policy

• Determines how long RMAN retains backups. You can configure it to keep backups for a specific number of days (recovery window) or by the number of backup copies (redundancy).

Command to view current retention policy:
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RMAN> SHOW RETENTION POLICY;

Command to configure retention policy:
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RMAN> CONFIGURE RETENTION POLICY TO REDUNDANCY 2;

RMAN> CONFIGURE RETENTION POLICY TO RECOVERY WINDOW OF 7 DAYS;

b. Backup Optimization

• Enables RMAN to skip backups of files that haven’t changed since the last backup. This is useful in environments where datafiles do not change frequently.

Command to view backup optimization setting:
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RMAN> SHOW BACKUP OPTIMIZATION;

Command to configure backup optimization:
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RMAN> CONFIGURE BACKUP OPTIMIZATION ON;

c. Default Device Type

• Specifies the default device for backups (e.g., disk or tape).

Command to view default device type:
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RMAN> SHOW DEFAULT DEVICE TYPE;

Command to configure the default device type:
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RMAN> CONFIGURE DEFAULT DEVICE TYPE TO DISK;

d. Control File Autobackup

• Ensures RMAN automatically backs up the control file and server parameter file (SPFILE) after every backup and database structural change (e.g., adding a tablespace).

Command to view control file autobackup setting:
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RMAN> SHOW CONTROLFILE AUTOBACKUP;

Command to configure control file autobackup:
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RMAN> CONFIGURE CONTROLFILE AUTOBACKUP ON;

e. Encryption Algorithm

• Specifies the encryption algorithm to use for backups. RMAN supports different encryption algorithms for backup security.

Command to view encryption algorithm:
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RMAN> SHOW ENCRYPTION ALGORITHM;

Command to configure encryption algorithm:
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RMAN> CONFIGURE ENCRYPTION ALGORITHM 'AES256';

f. Compression Algorithm

• Defines the algorithm RMAN uses to compress backups, saving storage space.

Command to view compression algorithm:
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RMAN> SHOW COMPRESSION ALGORITHM;

Command to configure compression algorithm:
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RMAN> CONFIGURE COMPRESSION ALGORITHM 'BASIC';

g. Channel Configuration

• Defines specific settings for RMAN channels, such as device type and degree of parallelism for backups.

Command to view channel configuration:
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RMAN> SHOW CHANNEL DEVICE TYPE DISK;

Command to configure channels:
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RMAN> CONFIGURE CHANNEL DEVICE TYPE DISK PARALLELISM 2;

RMAN> CONFIGURE CHANNEL DEVICE TYPE SBT PARALLELISM 4;

h. Snapshot Control File Location

• Specifies the location where RMAN stores the snapshot control file. RMAN uses this file during backup and recovery operations.

Command to view snapshot control file location:
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RMAN> SHOW SNAPSHOT CONTROLFILE NAME;

Command to configure snapshot control file location:
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RMAN> CONFIGURE SNAPSHOT CONTROLFILE NAME TO '/u01/backup/snapshot.ctl';

i. Archived Redo Logs Deletion Policy

• Specifies when RMAN can delete archived redo logs after backing them up.

Command to view deletion policy for archived logs:
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RMAN> SHOW ARCHIVELOG DELETION POLICY;

Command to configure deletion policy:
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RMAN> CONFIGURE ARCHIVELOG DELETION POLICY TO BACKED UP 1 TIMES TO DISK;

j. Auxiliary Destination

• Specifies the destination for duplicate databases and temporary storage during database duplication or recovery.

Command to view auxiliary destination:
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RMAN> SHOW AUXILIARY DESTINATION;

Command to configure auxiliary destination:
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RMAN> CONFIGURE AUXILIARY DESTINATION TO '/u01/aux';

k. Automatic Backup of SPFILE

• This ensures that the SPFILE is backed up with the control file automatically.

Command to view SPFILE autobackup setting:
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RMAN> SHOW CONTROLFILE AUTOBACKUP FORMAT FOR DEVICE TYPE DISK;

3. Example of SHOW ALL Output

When you execute the SHOW ALL command, you’ll see an output like this:

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RMAN configuration parameters are:

CONFIGURE RETENTION POLICY TO REDUNDANCY 2;

CONFIGURE BACKUP OPTIMIZATION ON;

CONFIGURE DEFAULT DEVICE TYPE TO DISK;

CONFIGURE CONTROLFILE AUTOBACKUP ON;

CONFIGURE CONTROLFILE AUTOBACKUP FORMAT FOR DEVICE TYPE DISK TO '/backup/cf_%F';

CONFIGURE CHANNEL DEVICE TYPE DISK FORMAT '/backup/db_%U';

CONFIGURE MAXSETSIZE TO UNLIMITED;

CONFIGURE ENCRYPTION ALGORITHM 'AES256';

CONFIGURE COMPRESSION ALGORITHM 'BASIC';

CONFIGURE DATAFILE BACKUP COPIES FOR DEVICE TYPE DISK TO 1;

CONFIGURE ARCHIVELOG BACKUP COPIES FOR DEVICE TYPE DISK TO 1;

CONFIGURE ARCHIVELOG DELETION POLICY TO NONE;

CONFIGURE SNAPSHOT CONTROLFILE NAME TO '/u01/app/oracle/dbs/snapcf_orcl.f';

4. Resetting Parameters to Default

• If you want to reset any parameter to its default value, you can use the CONFIGURE ... CLEAR command.

Command to reset a specific parameter:
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RMAN> CONFIGURE RETENTION POLICY CLEAR;

RMAN> CONFIGURE CHANNEL DEVICE TYPE DISK CLEAR;

RMAN> CONFIGURE <parameter_name> CLEAR; 

Using the SHOW ALL and CONFIGURE commands, you can control and monitor all aspects of RMAN backup configuration, tailoring it to meet your environment's needs.

RMAN BACKUP

RMAN (Recovery Manager) is an Oracle Database utility that allows you to back up, restore, and recover data files, control files, and archived redo logs. It's a key tool for managing Oracle database backups. Here’s an overview of RMAN backup concepts and processes:

1. Types of RMAN Backups

• Full Backup: Backs up all the data in the database or selected tablespaces/datafiles. It does not mark the backed-up blocks as backed up (unlike incremental backups).

• Incremental Backup: Backs up only the data blocks that have changed since the last backup. It has two levels:

  • Level 0: A full backup of the database, similar to a full backup.

  • Level 1: Backs up only the data blocks changed since the previous Level 0 or Level 1 backup.

• Cumulative Backup: A type of incremental backup that backs up all changes since the last Level 0 backup.

• Differential Backup: Backs up changes since the last Level 1 incremental backup.

2. Basic RMAN Backup Commands

Full Database Backup:
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RMAN> BACKUP DATABASE;

Incremental Level 0 Backup:
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RMAN> BACKUP INCREMENTAL LEVEL 0 DATABASE;

Incremental Level 1 Backup (Differential):
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RMAN> BACKUP INCREMENTAL LEVEL 1 DATABASE;

Incremental Level 1 Backup (Cumulative):
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RMAN> BACKUP INCREMENTAL LEVEL 1 CUMULATIVE DATABASE;

Backup of Specific Tablespaces:
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RMAN> BACKUP TABLESPACE users, system;

Backup of Control File and SPFILE:
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RMAN> BACKUP CURRENT CONTROLFILE;

RMAN> BACKUP SPFILE;

Archivelog Backup:
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RMAN> BACKUP ARCHIVELOG ALL;

3. Backup Locations

Disk: RMAN stores backups on a local or network disk.
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RMAN> BACKUP DATABASE FORMAT '/backup/%d_db_%u_%s.bkp';

Tape (SBT): Backup to tape using a media manager.
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RMAN> BACKUP DATABASE DEVICE TYPE sbt;

4. Backup Verification

RMAN allows you to verify backups without restoring them:

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RMAN> RESTORE DATABASE VALIDATE;

5. Crosscheck and Delete Expired Backups

Crosscheck: Verifies the status of backups, ensuring that they are still available.
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RMAN> CROSSCHECK BACKUP;

Delete Expired Backups: Deletes backups marked as expired.
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RMAN> DELETE EXPIRED BACKUP;

6. Backup Optimization

Backup optimization avoids backing up unchanged files:

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RMAN> CONFIGURE BACKUP OPTIMIZATION ON;

7. Encrypted Backups

RMAN supports encrypted backups for data security:

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RMAN> BACKUP AS COMPRESSED BACKUPSET DATABASE ENCRYPTION;

8. Backup Compression

RMAN can compress backups to save storage:

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RMAN> CONFIGURE COMPRESSION ALGORITHM 'BASIC';

RMAN> BACKUP AS COMPRESSED BACKUPSET DATABASE;

9. Monitoring and Reporting

List Backups:
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RMAN> LIST BACKUP;

RMAN Backup Report:
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RMAN> REPORT NEED BACKUP;

Best Practices for RMAN Backup:

1. Implement Incremental Backups: Reduce backup time and space by using incremental backups.

2. Test Backup Restoration: Periodically test backups by restoring them to ensure they are reliable.

3. Use Multiple Backup Locations: Store backups on both disk and tape for redundancy.

4. Use Retention Policies: Set up proper retention policies based on recovery needs.

5. Use Compression and Encryption: Optimize storage and enhance security with compression and encryption techniques.

Maintaining Oracle RMAN 

Maintaining Oracle RMAN (Recovery Manager) backups involves various tasks that ensure the health and reliability of your backups. Proper maintenance helps in optimizing backup performance, managing storage, and ensuring backups are available for recovery when needed. Here are key Oracle RMAN maintenance tasks:

1. Crosschecking Backups

• Crosschecking backups ensures that the backups stored in RMAN's metadata repository (control file or recovery catalog) exist physically at the specified location. If a backup is missing or inaccessible, RMAN marks it as EXPIRED.

Command:
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RMAN> CROSSCHECK BACKUP;

RMAN> CROSSCHECK ARCHIVELOG ALL;

2. Deleting Obsolete Backups

• RMAN keeps track of backups that are no longer needed based on the configured retention policy (either recovery window or redundancy). You can safely delete obsolete backups to free up storage.

Command:
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RMAN> DELETE OBSOLETE;

• The command checks against the retention policy and deletes any backups that no longer meet the policy.

3. Deleting Expired Backups

• Backups marked as EXPIRED (i.e., missing or unavailable) should be deleted from RMAN's metadata repository.

Command:
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RMAN> DELETE EXPIRED BACKUP;

4. Cataloging Backups

• If backups are moved manually (e.g., from one disk location to another) or created outside RMAN, you need to catalog them into RMAN’s metadata so RMAN can track and use them for restores.

Command:
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RMAN> CATALOG START WITH '/path/to/backup/';

RMAN> CATALOG BACKUPPIECE '/path/to/backupfile.bkp';

5. Backup Validation

• Validating backups ensures that the backup files are usable for recovery without actually restoring them. This process checks for corruption or missing blocks.

Command:
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RMAN> VALIDATE BACKUPSET;

RMAN> VALIDATE DATABASE;

• Regular validation is important for confirming the integrity of your backups.

6. Backup Compression and Optimization

• RMAN allows the configuration of compression to reduce the size of backups and optimization to avoid backing up unchanged data.

Enable Backup Compression:
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RMAN> CONFIGURE COMPRESSION ALGORITHM 'BASIC';

7. Managing the Flash Recovery Area (FRA)

• If you're using the Flash Recovery Area (FRA) for RMAN backups, it's crucial to monitor its space usage and clear obsolete files. The FRA automatically manages space, but it can fill up if not monitored.

Command to show FRA usage:
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SQL> SELECT * FROM V$RECOVERY_FILE_DEST;

Command to delete obsolete files in the FRA:
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RMAN> DELETE OBSOLETE RECOVERY AREA;

8. Backup Retention Policy

• Review and configure your RMAN retention policy to ensure backups are retained only as long as necessary.

Set retention by number of backups:
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RMAN> CONFIGURE RETENTION POLICY TO REDUNDANCY 2;

Set retention by recovery window:
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RMAN> CONFIGURE RETENTION POLICY TO RECOVERY WINDOW OF 7 DAYS;

9. Monitoring and Reporting

• RMAN provides several reporting options to help you understand the status of your backups and identify any potential issues.

List Backups:
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RMAN> LIST BACKUP;

RMAN> LIST BACKUP SUMMARY;

Generate Reports (e.g., backups that need to be taken, datafiles at risk):
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RMAN> REPORT NEED BACKUP;

• RMAN> REPORT OBSOLETE;

About Differential Incremental Backups