Question

oracle 数据库开启的简单问题

startup = startup nomount + alter database mount + alter database open；
startup mount = startup nomount + alter database mount；
上面两个等式正确吗？

Answer 1

1 -- startup nomount ; alter database mount ;alter database open
2 -- startup mount ; alter database open
3 -- startup / startup open

追问

也就是说是一样的、
问下：热备后是不是要执行alter system archive log current或者alter system swith logfile 、
还是都要执行，执行几遍？
谢了！

追答

1、oracle开启归档模式 ：
startup mount;
alter database archivelog;
alter database open;
2、检查是否归档模式：
archive log list;
3、双机热备时为了保证数据的完整和一致。执行alter system archive log current和alter system swith logfile。区别在于:
ALTER SYSTEM SWITCH LOGFILE对单实例数据库或RAC中的当前实例执行日志切换;
ALTER SYSTEM ARCHIVE LOG CURRENT会对数据库中的所有实例执行日志切换。

追问

都已经对所有日志切换了 为什么还要进行当前日志切换、
所有日志切换一遍，当前切换3遍？

追答

我想你最好读一下原版的解释。
ALTER SYSTEM SWITCH LOGFILE ;
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 ;
Specify CURRENT to manually archive the current redo log file group of the specified thread（instance）, forcing a log switch. If you omit the THREAD parameter, then Oracle archives all redo log file groups from all enabled threads（instances）, including logs previous to current logs. You can specify CURRENT only when the database is open.
ALTER SYSTEM ARCHIVE LOG CURRENT NOSWITCH;
Specify NOSWITCH if you want to manually archive the current redo log file group without forcing a log switch.

Answer 2

是一样的，等式正确

追问

问下：热备后是不是要执行alter system archive log current或者alter system swith logfile 、
还是都要执行，执行几遍？
谢了！