What is the difference between online and offline backups

cneo2012

于 2007-12-31 20:20:47 发布

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文章标签：数据库

本文详细介绍了数据库的在线(热)备份与离线(冷)备份的概念及区别。在线备份是在数据库正常运行的情况下进行的，适用于归档模式；而离线备份则需要数据库关闭，不论数据库是否处于归档模式均可进行。离线备份恢复较为简单，无需通过归档日志恢复数据一致性，但会造成数据库不可用的时间较长。在线备份虽然不会导致服务中断，但实施过程更为复杂。

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摘自orafaq

A hot (or on-line) backup is a backup performed while the database is open and available for use (read and write activity). Except for Oracle exports, one can only do on-line backups when the database is ARCHIVELOG mode.

A cold (or off-line) backup is a backup performed while the database is off-line and unavailable to its users. Cold backups can be taken regardless if the database is in ARCHIVELOG or NOARCHIVELOG mode.

It is easier to restore from off-line backups as no recovery (from archived logs) would be required to make the database consistent. Nevertheless, on-line backups are less disruptive and doesn't require database downtime.

Point-in-time recovery (regardless if you do on-line or off-line backups) is only available when the database is in ARCHIVELOG mode.

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