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ALTER SYSTEM SWITCH LOGFILE VS ALTER SYSTEM ARCHIVE LOG CURRENT

原创 Linux操作系统 作者:cc59 时间:2006-07-07 00:00:00 0 删除 编辑


ALTER SYSTEM SWITCH LOGFILE ;

SWITCH LOGFILE Clause

The SWITCH LOGFILE clause lets you explicitly force Oracle to begin writing to a new redo log file group, regardless of whether the files in the current redo log file group are full. When you force a log switch, Oracle begins to perform a checkpoint but returns control to you immediately rather than when the checkpoint is complete. To use this clause, your instance must have the database open.

ALTER SYSTEM ARCHIVE LOG CURRENT ;CURRENT Clause

Specify CURRENT to manually archive the current redo log file group of the specified thread, forcing a log switch. If you omit the THREAD parameter, then Oracle archives all redo log file groups from all enabled threads, including logs previous to current logs. You can specify CURRENT only when the database is open.

ALTER SYSTEM ARCHIVE LOG CURRENT NOSWITCH;NOSWITCH

Specify NOSWITCH if you want to manually archive the current redo log file group without forcing a log switch. This setting is used primarily with standby databases to prevent data divergence when the primary database shuts down. Divergence implies the possibility of data loss in case of primary database failure.

You can use the NOSWITCH clause only when your instance has the database mounted but not open. If the database is open, then this operation closes the database automatically. You must then manually shut down the database before you can reopen it.

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