Oracle Solution for Error ora-12526

ORA-12526: TNS:listener: all appropriate instances are in restricted mode

What triggered the Error:

Database instances supporting the service requested by the client were in restricted mode. The Listener does not allow connections to instances in restricted mode. This condition may be temporary, such as during periods when database administration is performed.

What should we do to fix it:

Attempt the connection again. If error persists, then contact the database administrator to change the mode of the instance, if appropriate.