Oracle in a Nutshell

Backup and Recovery Fundamentals

The common Oracle backup and recovery methods can be differentiated in a number of ways, based on the type of backup and recovery available and the steps necessary to recover from a failure. The following list summarizes the concepts and terms that are fundamental to the backup and recovery process.

Instance/media recovery

An Oracle database can fail in two basic ways: instance failure and media failure. When instance failure occurs, something happens that prevents the processes that make up an Oracle instance from servicing database requests. The Oracle database can automatically recover itself from this type of failure as soon as the instance is restarted, with roll-forward and rollback operations. Because instance recovery is automatic, we don’t cover it in this chapter.

An Oracle database can also experience a media failure. This occurs when the underlying storage for the files used by an Oracle database fails or experiences a corruption. Oracle does not provide automatic recovery from this type of failure, because there may very well be other actions that you need to take before you attempt recovery, such as replacing a failed disk drive. The backup and recovery operations described in the remainder of this chapter are used to address media failure.

Consistent/inconsistent

An Oracle backup can be either consistent or inconsistent. A consistent backup is a complete backup of an Oracle database that is in a consistent state. A consistent backup ...