ORA-12537: TNS:connection closed


Sometimes You can get “ORA-12537: TNS:connection closed” error.


Details of error are as follows.

TNS-00584: Valid node checking configuration error

Cause: Valid node checking specific Oracle Net configuration is invalid.

Action: Ensure the hosts specified in the “invited_nodes” and “excluded_nodes” are valid.

For further details, turn on tracing and reexecute the operation.

    TNS-12532: TNS:invalid argument
    TNS-12560: TNS:protocol adapter error
    TNS-502: Invalid argument
    32-bit Windows Error: 515: Unknown error

    Error listening on: (ADDRESS=(PROTOCOL=TCP)(Host=<hostname>)(Port=1562))
    TNS-12560: TNS:protocol adapter error 
    TNS-00584: Valid node checking configuration error

   Connecting to (ADDRESS=(PROTOCOL=TCP)(Host=hostname)(Port=1521))
   TNS-12537: TNS:connection closed
   TNS-12560: TNS:protocol adapter error
   TNS-00507: Connection closed



This error is related with the Permission or ownership or group permission, so check them if they are ok or not.

Check permission.

[oracle@msdbadm01 ~]$ ll $ORACLE_HOME/bin/oracle
-rwsr-s--x. 1 oracle oinstall 239952653 Sep 11 20:36 /u01/app/oracle/product/12.1.2/dbhome_1/bin/oracle


Revoke the user execution permission from $ORACLE/bin/oracle as follows.

[oracle@msdbadm01 ~]$  chmod 6751 $ORACLE_HOME/bin/oracle

[oracle@msdbadm01 ~]$ ll $ORACLE_HOME/bin/oracle
-rwSr-s--x. 1 oracle oinstall 239952653 Sep 11 20:36 /u01/app/oracle/product/12.1.2/dbhome_1/bin/oracle


Or the second case of this error is as follows.

There is an invalid hostname in the TCP.INVITED_NODES list in the sqlnet.ora file.

Oracle no longer  allows  the listener to startup if an invalid hostname or ip address is specified in the invited_nodes list.  The listener will not start if any of the hosts or ip addresses are note resolvable.   The only solution to this issue is to ensure that all the hostnames and ip addresses in the invited nodes list are resolvable using ping or nslookup from the host where the listener is starting.

In some cases, the localhost might cause this behavior.


To solve this error, go to sqlnet.ora and check and fix the right INVITED_NODES IP as follows,

[oracle@msdbadm01 ~]$ cd $ORACLE_HOME/network/admin
[oracle@msdbadm01 admin]$ vi sqlnet.ora 





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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