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';


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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