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Title
Error, "ORA-12547 : TNS lost contact" when trying to connect to database -
Description
The following error occurs when trying to connect to Oracle database:
ORA-12547 : TNS lost contact -
Cause
Client was blocked to connect to the database based on their IP address or hostname by using the parameter below in the SQLNET.ORA file of the Database Server.
tcp.validnode_checking = YES -
Resolution
Change the parameter below to NO in the SQLNET.ORA file of the Database Server to turn off the blocking.
tcp.validnode_checking = NO
NOTE: This will turn off some security features on the database, check with an Oracle DBA to consult the best workaround for the issue.