ORA-12537: TNS:connection closed – When Nothing Else Works!

Posted in: Oracle, Technical Track

When you’re sure all the TNS listener (SID_LIST_LISTENER in this case) services and db_domain are fine, but you still face the ORA-12537: TNS:connection closed error when trying to remotely access an open database, what can you do next?

[oracle@pythiansrv admin]$ sqlplus sys/******@MYDB as sysdba

SQL*Plus: Release Production on Wed Feb 3 17:45:29 2021

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ORA-12537: TNS:connection closed

Here’s a quick tip — if you’ve been an Oracle DBA for long enough, you’ll know this workaround solves a variety of issues:

[oracle@pythiansrv admin]$ cd $ORACLE_HOME/bin
[oracle@pythiansrv bin]$ ls -lrt oracle
-rwxr-x--x. 1 oracle oinstall 242993632 Dec 18 19:20 oracle
[oracle@pythiansrv bin]$ chmod 6751 oracle
[oracle@pythiansrv bin]$ ls -lrt oracle
-rwsr-s--x. 1 oracle oinstall 242993632 Dec 18 19:20 oracle

As you can see, the CHMOD 6751 did it again!

The reason this happened to me is, somehow, these permissions were wrong in my LOCAL host (the one I was trying to use the SQLPlus* from).

I hope my experience helps you. If you have any questions or anything to add, please leave me a comment.

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About the Author

Lead Database Consultant
Well known in the Oracle community in Latin America and Europe where he participates regularly in technology events, Matheus is actually the youngest Oracle ACE Director in the world. Lead Database Consultant at Pythian, Matheus is a Computer Scientist by PUCRS and has been working as an Oracle DBA for the last 10 years.

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