在只读模式下，数据文件及联机日志文件都禁止写操作。不过允许执行数据库恢复及其他不会产生回滚的操作。
数据库关闭的情况下
[oracle@prod1 ~]$ sqlplus / as sysdba SQL*Plus: Release 11.2.0.1.0 Production on Sun Feb 22 19:07:12 2015 Copyright (c) 1982, 2009, Oracle. All rights reserved. Connected to an idle instance. idle> startup open read only; ORACLE instance started. Total System Global Area 891383808 bytes Fixed Size 1340104 bytes Variable Size 658509112 bytes Database Buffers 226492416 bytes Redo Buffers 5042176 bytes Database mounted. Database opened. idle> select open_mode from v$database;OPEN_MODE --------------------READ ONLY
mount状态下
idle> alter database open read only; Database altered.
重新恢复到读写状态
idle> shutdown immediate; Database closed.Database dismounted.ORACLE instance shut down.idle> startup mount; ORACLE instance started.Total System Global Area 891383808 bytesFixed Size 1340104 bytesVariable Size 658509112 bytesDatabase Buffers 226492416 bytesRedo Buffers 5042176 bytesDatabase mounted.idle> alter database open read write; Database altered.
在只读模式下，数据文件及联机日志文件都禁止写操作。不过允许执行数据库恢复及其他不会产生回滚的操作。
数据库关闭的情况下
[oracle@prod1 ~]$ sqlplus / as sysdba SQL*Plus: Release 11.2.0.1.0 Production on Sun Feb 22 19:07:12 2015 Copyright (c) 1982, 2009, Oracle. All rights reserved. Connected to an idle instance. idle> startup open read only; ORACLE instance started. Total System Global Area 891383808 bytes Fixed Size 1340104 bytes Variable Size 658509112 bytes Database Buffers 226492416 bytes Redo Buffers 5042176 bytes Database mounted. Database opened. idle> select open_mode from v$database;OPEN_MODE --------------------READ ONLY
mount状态下
idle> alter database open read only; Database altered.
重新恢复到读写状态
idle> shutdown immediate; Database closed.Database dismounted.ORACLE instance shut down.idle> startup mount; ORACLE instance started.Total System Global Area 891383808 bytesFixed Size 1340104 bytesVariable Size 658509112 bytesDatabase Buffers 226492416 bytesRedo Buffers 5042176 bytesDatabase mounted.idle> alter database open read write; Database altered.
oracle怎么查询所有索引May 13, 2022 pm 05:23 PM方法：1、利用“select*from user_indexes where table_name=表名”语句查询表中索引；2、利用“select*from all_indexes where table_name=表名”语句查询所有索引。
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oracle全角怎么转半角May 13, 2022 pm 03:21 PM在oracle中，可以利用“TO_SINGLE_BYTE(String)”将全角转换为半角；“TO_SINGLE_BYTE”函数可以将参数中所有多字节字符都替换为等价的单字节字符，只有当数据库字符集同时包含多字节和单字节字符的时候有效。
Oracle怎么查询端口号May 13, 2022 am 10:10 AM在Oracle中，可利用lsnrctl命令查询端口号，该命令是Oracle的监听命令；在启动、关闭或重启oracle监听器之前可使用该命令检查oracle监听器的状态，语法为“lsnrctl status”，结果PORT后的内容就是端口号。
oracle怎么删除sequenceMay 13, 2022 pm 03:35 PM在oracle中，可以利用“drop sequence sequence名”来删除sequence；sequence是自动增加数字序列的意思，也就是序列号，序列号自动增加不能重置，因此需要利用drop sequence语句来删除序列。
oracle怎么查询数据类型May 13, 2022 pm 04:19 PM在oracle中，可以利用“select ... From all_tab_columns where table_name=upper('表名') AND owner=upper('数据库登录用户名');”语句查询数据库表的数据类型。
oracle查询怎么不区分大小写May 10, 2022 pm 05:45 PM方法：1、利用“LOWER(字段值)”将字段转为小写，或者利用“UPPER(字段值)”将字段转为大写；2、利用“REGEXP_LIKE(字符串,正则表达式,'i')”，当参数设置为“i”时，说明进行匹配不区分大小写。
Oracle怎么修改sessionMay 13, 2022 pm 05:06 PM方法：1、利用“alter system set sessions=修改后的数值 scope=spfile”语句修改session参数；2、修改参数之后利用“shutdown immediate – startup”语句重启服务器即可生效。
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