Database Reference
In-Depth Information
Chapter 3
User-Managed Backup and Recovery
All DBAs should know how to back up a database. Even more critical, a DBA must be able to restore and recover a
database. When media failures occur, everybody looks to the DBA to get the database up and running. There are two
common, yet very different, Oracle approaches for backup and recovery:
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User-managed approach
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RMAN approach
User-managed backups are aptly named because you manually perform all steps associated with the backup or
recovery, or both. There are two types of user-managed backups: cold backups and hot backups. Cold backups are
sometimes called offline backups because the database is shut down during the backup process. Hot backups are also
referred to as online backups because the database is available during the backup procedure.
RMAN is Oracle's flagship backup and recovery tool. It automates and manages most aspects of backup and
recovery. For Oracle backup and recovery, you should use RMAN. So, why have a chapter about user-managed
backups when this approach has been gathering dust for more than a decade? Consider the following reasons for
understanding user-managed backup and recovery:
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You still find shops using user-managed backup and recovery techniques. Therefore, you're
required to be knowledgeable about this technology.
•
Manually executing a user-managed backup, restore, and recovery solidifies your
understanding of the Oracle backup and recovery architecture. This helps immensely when
you're troubleshooting issues with any backup and recovery tool and lays the foundation of
core knowledge for key Oracle tools, such as RMAN and Data Guard.
•
You'll more fully appreciate RMAN and the value of its features.
•
Nightmarish database recovery stories recounted by the old DBAs will now make sense.
For these reasons, you should be familiar with user-managed backup and recovery techniques. Manually working
through the scenarios in this chapter will greatly increase your understanding of which files are backed up and how
they're used in a recovery. You'll be much better prepared to use RMAN. RMAN makes much of backup and recovery
automated and push-button. However, knowledge of how to back up and recover a database manually helps you think
through and troubleshoot issues with any type of backup technology.
This chapter begins with cold backups. These types of backups are viewed as the simplest form of user-managed
backup because even a system administrator can implement them. Next, the chapter discusses hot backups. You also
investigate several common restore-and-recovery scenarios. These examples build your base knowledge of Oracle
backup and recovery internals.
