Overview of Database Backup and Recovery - wykład

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Overview of Database Backup and Recovery
The focus in Oracle Database backup and recovery is on the physical backup of
database files, which permits you to reconstruct your database. RMAN, a
command-line tool, is the method preferred by Oracle for efficiently backing up and
recovering your Oracle database. The files protected by the backup and recovery
facilities built into RMAN include data files, control files, server parameter files, and
archived redo log files. With these files you can reconstruct your database. RMAN is
designed to work intimately with the server, providing block-level corruption
detection during backup and restore. RMAN optimizes performance and space
consumption during backup with file multiplexing and backup set compression, and
integrates with leading tape and storage media products. The backup mechanisms
work at the physical level to protect against file damage, such as the accidental
deletion of a data file or the failure of a disk drive. RMAN can also be used to perform
Logical backups, such as exporting database objects such as tables or tablespaces, are a
useful supplement to physical backups, but cannot protect your whole database. An
effective backup strategy must be based on physical backups.
The Oracle Database flashback features provide a range of physical and logical data
recovery tools as efficient, easy-to-use alternatives to physical and logical backups. The
flashback features enable you to reverse the effects of unwanted database changes
without restoring data files from backup.
This section introduces the following flashback features:
■ Oracle Flashback Table, which enables you to revert a table to its contents at a time
in the recent past
■ Oracle Flashback Drop, which enables you to retrieve deleted (dropped) database
■ Oracle Flashback Database, which enables you to revert the entire database to a
past point in time
The first two features operate at the logical level, whereas the last feature operates at
the physical level. None of the preceding features requires advance preparation such
as creating logical exports to allow for retrieval of your lost data, but Oracle Flashback
Database requires the advance preparation of enabling the feature. You can use all of
the features while your database is available. Oracle Database Backup and Recovery
User's Guide discusses the flashback features of Oracle Database at greater length.
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