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ORA-12547: TNS :lost contact when try to connect to Oracle

There could be many reasons for the above error, but one of the common issue is due to incorrect permissions to the oracle binaries in the $ORACLE_HOME/bin directory.

The “root.sh” is responsible to give the correct permissions to the oracle binaries during installation using Oracle Universal Installer (OUI). It is a mandatory step to execute the script as “root” user during installation. But later if you have messed up the permissions of the oracle binaries then you could execute it again and it should mostly fix the issue.


-sh-4.1$ ls -lrt oracle
-rwsr-s--x 1 oracle oinstall 228881982 Nov  2 11:19 oracle

The permissions should be -rwsr-s–x

If not, then change permission as below:

-sh-4.1$ cd $ORACLE_HOME/bin
-sh-4.1$ chmod 6751 oracle
-sh-4.1$ ls -lrt oracle

Try connecting now, hopefully ORA-12547 shouldn’t occur again. If the error still occurs, try executing “root.sh” in $ORACLE_HOME/bin.

Hope it helps!