ORA-12537: TNS:connection closed – When nothing else works!

Sounds desperate?

Well, when you are sure all the TNS, listener (SID_LIST_LISTENER on this case), services, db_domain are fine but still facing this issue when trying to access remotely an open database… what to do?

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

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

Copyright (c) 1982, 2013, Oracle. All rights reserved.

ORA-12537: TNS:connection closed

My friend here is a quick tip that, if you are an Oracle DBA for time enough you know that solves several issues, maybe affecting this case again:

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

The CHMOD 6751 did it again!

It happened to me because, somehow, these permissions were wrong in my LOCAL host (the one I was trying to use the SQLPlus* from.

I hope it helps!


“TNS-12531: TNS:cannot allocate memory error” – Are you sure, Oracle?

Hey guys!
So, I was working on a server build and everything was running fine until I tried to start the listerner. The process hang on “Starting /u01/app/grid/product/12.1.0/grid/bin/tnslsnr: please wait…” and then raised TNS-12531: TNS:cannot allocate memory error.

Well 1st thing, looked the error up using orerr:

TNS-12531: TNS: cannot allocate memory
Cause: Sufficient memory could not be allocated to perform the desired activity.
Action: Either free some resource for TNS, or add more memory to the machine. For further details, turn on tracing and re-execute the operation.

Should be simple right? Well, not in this case. The server had plenty of resources and not even the database was up yet so over 90% of the server memory was free.

Checked all sort of things when I started to check the server network configuration.
Looking up found that the server will through this error also when the hostname definition is different from what is resolved by the /etc/hosts file.

Once those matched, volià, listener started successfully.

Not the memory right? Oracle and its tricks…

That kept me bugging so I found this article, which shows a trace of the listener with a bit more information.

Hope this can save you some minutes on troubleshooting.

Until next time!