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Remote Connections Via the Listener to the Database Fail with TNS-12526, TNS-12527 or TNS-12528 (Doc ID 444120.1)

Last updated on FEBRUARY 22, 2019

Applies to:

Oracle Net Services - Version to [Release 10.2 to 12.2]
Information in this document applies to any platform.


Connections via the listener to an instance that is in RESTRICTED status or in NO MOUNT status may fail with TNS-12526, TNS-12527 or TNS-12528 even when supplying the credentials for a privileged account.    The lsnrctl services output will show that the service handler for this instance is in state: BLOCKED or RESTRICTED.

The full error text is:

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

ORA-12528 (TNS-12528)
TNS:listener: all appropriate instances are blocking new connections

ORA-12527 (TNS-12527)
TNS:listener: all instances are in restricted mode or blocking



The only significant change would be that the instance has been started up in some kind of "restricted access" mode such as RESTRICTED or NO MOUNT.

Here is an example of starting up the database in restricted mode and the output for lsnrctl status:

1.Start the database with restricted mode

SQL>startup restrict

2.Check the status of the listener

LSNRCTL> status
Connecting to (ADDRESS=(PROTOCOL=tcp)(HOST=<hostname>)(PORT=1521))
Version TNSLSNR for 32-bit Windows: Version
Start Date 21-JUL-2003 18:19:03
Uptime 2 days 17 hr. 36 min. 17 sec
Trace Level OFF
Security OFF
Listener Parameter File e:\10g\network\admin\listener.ora
Listener Log File e:\10g\network\log\listener.log
Listening Endpoints Summary...
Services Summary...
Service "<service.domain>" has 1 instance(s).
Instance "<instance>", status RESTRICTED, has 1 handler(s) for this service...
The command completed successfully


From the above we can see that the listener status for that instance is


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