Knowledge Base

First mount and than open the Oracle database before doing any database actions

ORA-01507: database not mounted

The database was not mounted.
In order to execute the command, the database needs to be mounted.

You can issue following command to mount the database:

alter database mount;

At mount phase, the Oracle controlfile(s) are read, which contain information about the database (such as the database name) and information about the datafiles and redolog files.

If there is a problem with (one of the) controlfile(s), the database can not be mounted until the problem is resolved.
Problems can be a missing or corrupt controlfile, a disk containing one of the controlfiles which is offline, …

To check what controlfiles are needed, you can issue following select

SQL> select value from v$parameter where name='control_files';

VALUE
--------------------------------------------------------------------------------
/u01/app/oracle/product/10.2.0/dbs/cntrlORA11G.dbf

Check the alert.log file for more information about problems, preventing the database from being mounted.

You can find detailed information about the Oracle startup sequence in the following information page.

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