UNDO_TABLESPACE-优快云博客

本文详细介绍了数据库中UNDOTABLESPACE参数的作用及其配置方法。该参数用于指定实例启动时所使用的撤销表空间。文章解释了如何设置此参数以及在不同情况下的默认行为，并提供了关于如何更换撤销表空间的信息。

UNDO_TABLESPACE

Property	Description
Parameter type	String
Syntax	`UNDO_TABLESPACE =` `undoname`
Default value	The first available undo tablespace in the database.
Modifiable	`ALTER SYSTEM`
Range of values	Legal name of an existing undo tablespace
Basic	Yes
Oracle RAC	Each instance must have a unique value for this parameter, when it is set.

UNDO_TABLESPACE specifies the undo tablespace to be used when an instance starts up. If this parameter is specified when the instance is in manual undo management mode, then an error will occur and startup will fail.

If the UNDO_TABLESPACE parameter is omitted, the first available undo tablespace in the database is chosen. If no undo tablespace is available, the instance will start without an undo tablespace. In such cases, user transactions will be executed using the SYSTEM rollback segment. You should avoid running in this mode under normal circumstances.

You can replace an undo tablespace with another undo tablespace while the instance is running.