How to Backup and Restore Oracle Database

Edited 1 week ago by ExtremeHow Editorial Team

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Oracle Database is a powerful and robust relational database management system. It is widely used by businesses and organizations around the world due to its ability to handle large amounts of data, deliver high performance, and provide comprehensive security features. To ensure data security, it is important to know how to backup and restore an Oracle database.

Backups are important because they allow us to recover data in case of data loss due to various reasons such as hardware failure, human error or software corruption. Similarly, the ability to restore a database from a backup is critical to ensure business continuity in such scenarios. Below, we will explore, in detail, the processes involved in backing up and restoring an Oracle database.

Introduction to backup and restore

To manage Oracle database backups, Oracle provides several utilities and methods. The two primary tools used for these tasks are Oracle Recovery Manager (RMAN) and Oracle Data Pump. Both have unique features and serve different purposes.

Oracle Recovery Manager (RMAN)

RMAN is a robust utility provided by Oracle to efficiently manage backup and recovery tasks. RMAN automates many of the processes involved in backup and recovery, ensures the integrity of database files, and provides the ability to perform incremental backups, which only copy the changes since the last backup.

Oracle Data Pump

Oracle Data Pump is used more for logical backups, which includes exporting and importing data and schema objects. It is useful for moving data between Oracle databases and archiving data.

Backup strategies

It is essential to have a well-defined backup strategy. Here are some common strategies for backing up Oracle databases:

Full database backup

It involves a total backup of the database including all data and structure. It is the simplest form of backup and allows complete restoration of the database. However, full backups for large databases can be time-consuming and resource-intensive.

Incremental backup

Incremental backups involve backing up only the data that has changed since the last backup. This approach is more efficient than full backups because it reduces the amount of data to be copied, saving both time and storage space.

Cumulative incremental backup

This type of backup copies all data that has changed since the last full backup, which differs from incremental backups that only capture changes since the last incremental backup. This strategy reduces restore time because fewer steps are required to restore the database.

Setting up RMAN for backup

Before using RMAN, make sure your environment is set up correctly. You must configure the Oracle Net Service Name for RMAN to connect to the target database. RMAN can be used through the command-line interface or Oracle Enterprise Manager. Here is a basic setup:

export ORACLE_HOME=/u01/app/oracle/product/12.2.0/dbhome_1 export ORACLE_SID=orcl rman target /

This connects RMAN to the database as the currently logged-in user.

Creating a full backup using RMAN

To take a full backup of a database using RMAN, you can use the following command:

RMAN> BACKUP DATABASE;

This command initiates a full backup of your database. RMAN makes copies of the data files, control files, and stored redo logs that are needed for recovery.

Incremental backup using RMAN

Incremental backup can be done using RMAN with the following command:

RMAN> BACKUP INCREMENTAL LEVEL 1 DATABASE;

This command creates an incremental backup of the database, capturing only the blocks that were modified since the last level 0 or level 1 backup.

Using Data Pump for logical backups

Oracle Data Pump is useful for logical backups, where specific data sets and schema objects are exported. Here's how to perform a full database export using Data Pump:

expdp username/password DIRECTORY=dpump_dir DUMPFILE=full.dmp FULL=Y LOGFILE=full.log

The above command exports the entire database to a dump file. Data Pump requires a directory object in Oracle, which acts as a pointer to a physical directory on the server's file system.

Restoring an Oracle database

Restoring using RMAN

Restoring a database means bringing back data from a backup. RMAN makes the restore process quite simple. Here is a typical restore command for full database recovery:

RMAN> RESTORE DATABASE; RMAN> RECOVER DATABASE;

This process involves restoring the data files and subsequently applying any stored redo logs to bring the database to a consistent state.

Restoring specific tablespaces or data files

RMAN also allows the restoration of specific tablespaces or data files. For example, to restore a particular tablespace, do the following:

RMAN> RESTORE TABLESPACE users; RMAN> RECOVER TABLESPACE users;

This command will restore and then recover the specified tablespace.

Database point-in-time recovery (PITR)

Point-in-time recovery is important in situations where errors need to be corrected, such as accidental deletion of data. RMAN allows recovering a database to a specific point in time with the following command:

RMAN> RUN { SET UNTIL TIME 'YYYY-MM-DD:HH24:MI:SS'; RESTORE DATABASE; RECOVER DATABASE; }

Make sure the correct time point is specified to avoid data loss in new transactions.

Using Data Pump for data restore

Restoring using Data Pump involves importing data from a dump file into the database. Here is an example of using Data Pump to import a dump file:

impdp username/password DIRECTORY=dpump_dir DUMPFILE=full.dmp LOGFILE=import.log FULL=Y

Data Pump can also import specific schemas or tables by setting the corresponding parameters. Data import manages data and schema restoration, allowing users to sync the database to its previous state according to the dump file.

Conclusion

Backup and restoration are important aspects of database administration. Understanding how to effectively use tools such as RMAN and Oracle Data Pump ensures that Oracle databases are adequately protected against data loss and can be restored quickly when needed. While RMAN is excellent for physical backup and recovery, Data Pump provides flexibility for logical data export and import.

Always remember to test your backup and recovery procedures regularly. This practice ensures that when disaster strikes, the recovery process is smooth and data loss is minimized as much as possible. Database administrators should also stay abreast of the latest developments and updates in Oracle technologies to continually enhance database management practices.

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