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Oracle backup methods

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One of the most important jobs / responsibilities of an Oracle database administrator, is to protect and safeguard all databases so that there is no data loss or corruption at any case.
Even at extreme conditions (physical disaster, deletion) an administrator is responsible for taking all measures and precautions in order to recover and restore the databases to a fully functional and operational state.

Oracle offers the following ways to backup / restore databases
1) Backup by putting the database in ARCHIVELOG mode.
2) By using the "RMAN"  with offline or on-line databases.
3) Backup all data and logs, by shutting down the database first, also known as cold / offline backups.
4) Export / Import ( imp / exp commands) by which tables and their structure is extracted and stored or  
    imported back to the database. In this case under normal circumstances one should use the same user for
    both tasks.
All the above methods are useful and meaningful to use depending on what kind of protection you might need.

In productive environments a combination of all the above is often used, since different features / alternatives are offered by each one of them.

Incremental or Full Backup?
Using the incremental or full backup method, depends totally on the strategy and specific needs of each system.
One should use incremental backups to save time and storage space on the backup media or when there is a limited bandwidth network.
Full backup has the advantage that all the data is backed up and restored once.
When using incremental backup methods, first you need to do a restore using a full backup set and then all the incremental backup sets taken after that one by one.

When in ARCHIVELOG mode incremental backups can be made while the database is open, otherwise first you have to shutdown the database.

Disaster recovery should be the very next step considered, in order to safe-guard the data and ensure fast and reliable recovery at any case.
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Author:George K.
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