Oracle Error ORA-12527: TNS:listener: all instances are in restricted mode or blocking new connections

Oracle Error Message

ORA-12527: TNS:listener: all instances are in restricted mode or blocking new connections

Reason for the Error

All appropriate database instances supporting the service requested by the client reported that they either were in restricted mode or were blocking the new connections. The Listener does not allow connections to such instances. This condition may be temporary, such as at instance startup.

Solution

Attempt the connection again. If error persists, then contact the database administrator to check the status of the instances.