TNS-12561: TNS unknown error


Sometimes You can get “TNS-12561: TNS:unknown error ” error.


Details of error are as follows.

TNS-12561: TNS:unknown error
Cause: A generic protocol error occurred.
Action: For further details, turn on tracing and reexecute the operation.




1. If there is connectivity with SSL via the TNS Listener to the Database locally, this indicates something on the “AWS” side is at fault.

2. If a program is scanning the Listener, it should not be making connection attempts or pings as a non-Oracle (Listener) user.


1. Check with the AWS (Amazon) technical vendor as to what may be wrong.

2. Make sure non-Oracle Client programs or processes are attempting to ping or “connect” to a secure Listener.
As a reference for fault finding any “<unknown connect data>” listener log entries, see the following:
Listener Log Intermittently Reports: <unknown connect data> and either * 12537 or * 12569 errors (Doc ID 1664901.1)


Do you want to learn more details about RMAN, then read the following articles.


About Mehmet Salih Deveci

I am Founder of SysDBASoft IT and IT Tutorial and Certified Expert about Oracle & SQL Server database, Goldengate, Exadata Machine, Oracle Database Appliance administrator with 10+years experience.I have OCA, OCP, OCE RAC Expert Certificates I have worked 100+ Banking, Insurance, Finance, Telco and etc. clients as a Consultant, Insource or Outsource.I have done 200+ Operations in this clients such as Exadata Installation & PoC & Migration & Upgrade, Oracle & SQL Server Database Upgrade, Oracle RAC Installation, SQL Server AlwaysOn Installation, Database Migration, Disaster Recovery, Backup Restore, Performance Tuning, Periodic Healthchecks.I have done 2000+ Table replication with Goldengate or SQL Server Replication tool for DWH Databases in many clients.If you need Oracle DBA, SQL Server DBA, APPS DBA,  Exadata, Goldengate, EBS Consultancy and Training you can send my email adress [email protected].-                                                                                                                                                                                                                                                 -Oracle DBA, SQL Server DBA, APPS DBA,  Exadata, Goldengate, EBS ve linux Danışmanlık ve Eğitim için  [email protected] a mail atabilirsiniz.

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