ORA-12547: TNS:lost contact Error

When I connect to Oracle database, I got ” ORA-12547: TNS:lost contact ” error.

ORA-12547: TNS:lost contact

Details of error are like following.

[oracle@MehmetSalih ~]$ sqlplus mehmet/mehmet@PRELIVE

SQL*Plus: Release 12.1.0.2.0 Production on Thu Aug 1 16:16:23 2019

Copyright (c) 1982, 2014, Oracle. All rights reserved.

ERROR:
ORA-12547: TNS:lost contact


Enter user-name: ^C
[oracle@MehmetSalih ~]$

TNS:lost contact

This ORA-12547: TNS:lost contact error is related with the tcp.validnode_checking = yes in sqlnet.ora file.

To solve this problem, firstly check sqlnet.ora file.

[oracle@MehmetSalih PRELIVE_MehmetSalih]$ cat sqlnet.ora
###############################################################
#
# Do not edit settings in this file manually. They are managed
# automatically and will be overwritten when AutoConfig runs.
# For more information about AutoConfig, refer to the Oracle
# E-Business Suite Setup Guide.
#
#$Header: NetServiceHandler.java 120.28.12020000.2 2012/07/05 11:52:15 brayasam ship $
#
###############################################################

NAMES.DIRECTORY_PATH=(TNSNAMES, ONAMES, HOSTNAME)
SQLNET.EXPIRE_TIME= 10
tcp.validnode_checking = yes
tcp.invited_nodes=(MehmetSalih.Deveci.local)
SQLNET.INBOUND_CONNECT_TIMEOUT =60


IFILE=/data/oracle/PRELIVE/12.1.0/network/admin/PRELIVE_MehmetSalih/sqlnet_ifile.ora
[oracle@MehmetSalih PRELIVE_MehmetSalih]$

You should remove tcp.validnode_checking = yes and tcp.invited_nodes=(MehmetSalih.Deveci.local) entries.

[oracle@MehmetSalih PRELIVE_MehmetSalih]$ vi sqlnet.ora
[oracle@MehmetSalih PRELIVE_MehmetSalih]$
[oracle@MehmetSalih PRELIVE_MehmetSalih]$



After remove related parameters, sqlnet.ora file should be like following.


[oracle@MehmetSalih PRELIVE_MehmetSalih]$ cat sqlnet.ora
###############################################################
#
# Do not edit settings in this file manually. They are managed
# automatically and will be overwritten when AutoConfig runs.
# For more information about AutoConfig, refer to the Oracle
# E-Business Suite Setup Guide.
#
#$Header: NetServiceHandler.java 120.28.12020000.2 2012/07/05 11:52:15 brayasam ship $
#
###############################################################

NAMES.DIRECTORY_PATH=(TNSNAMES, ONAMES, HOSTNAME)
SQLNET.EXPIRE_TIME= 10
SQLNET.INBOUND_CONNECT_TIMEOUT =60


IFILE=/data/oracle/PRELIVE/12.1.0/network/admin/PRELIVE_MehmetSalih/sqlnet_ifile.ora
[oracle@MehmetSalih PRELIVE_MehmetSalih]$

ORA-12547

To solve this error, Now reload or stop start Listener. Login database via sqlplus or Toad like following.

Problem has been solved.

[oracle@MehmetSalih ~]$ sqlplus mehmet/mehmet@PRELIVE

SQL*Plus: Release 12.1.0.2.0 Production on Thu Aug 1 16:33:34 2019

Copyright (c) 1982, 2014, Oracle. All rights reserved.

Last Successful login time: Thu Aug 01 2019 17:24:06 +03:00

Connected to:
Oracle Database 12c Enterprise Edition Release 12.1.0.2.0 - 64bit Production
With the Partitioning, OLAP, Advanced Analytics and Real Application Testing options

Sometimes oracle.exe or oracle executable file’s permission may be modified

Check oracle like following.

[oracle@MehmetSalih ~]$ cd $ORACLE_HOME/bin
[oracle@MehmetSalih bin] $ ls -ltr oracle
[oracle@MehmetSalih bin] $ -rwx-xr-x 1 oracle oinstall 136803483 Jul 16 10:24 oracle

Change permissions and give 6751 permission as below:

[oracle@MehmetSalih bin] $ chmod 6751 oracle
[oracle@MehmetSalih bin] $ ls -ltr oracle
-rwsr-s--x 1 oracle oinstall 136803483 Jul 16 10:24 oracle

Other case I have seen that extra slash usage with Oracle home as follows 🙂

/u01/app/oracle/product/18.0/dbhome_1/

To solve this problem check your Oracle home’s extra slash and remove it 😉 use as follows without slash.

/u01/app/oracle/product/18.0/dbhome_1

Do you want to learn Oracle Database for Beginners, then Click and read the following articles.

Oracle Database Tutorials for Beginners ( Junior Oracle DBA )