How to open a database from read write mode to mount status

 SQL> select name,open_mode from v$database;

NAME      OPEN_MODE

--------- --------------------

ORCL      READ WRITE

SQL> alter database mount;

alter database mount

*

ERROR at line 1:

ORA-01100: database already mounted

# So here we get the error database is already mounted, in this case we need to ensure the database is shutdown first and then only we can mount the database.

SQL> shu immediate

Database closed.

Database dismounted.

ORACLE instance shut down.

# So lets see how we can do it

SQL> startup mount

ORACLE instance started.

Total System Global Area 1073740680 bytes

Fixed Size                  9694088 bytes

Variable Size             306184192 bytes

Database Buffers          754974720 bytes

Redo Buffers                2887680 bytes

Database mounted.

SQL> SQL>

SQL> select name,open_mode from v$database;

NAME      OPEN_MODE

--------- --------------------

ORCL      MOUNTED

# With this we know how we can mount the database from open state.