Sunday, November 18, 2007
ORA-12537 TNS: Connection Closed
Dear readers, When I was trying to establish client connection to one of our databases running on Oracle 10g, I received “ORA-12537 TNS: Connection Closed” error. Upon investigation, I came across “TCP.VALIDNODE_CHECKING” parameter in “sqlnet.ora” file. This was set to “YES”. I simply commented this parameter and every thing went fine. Clients were able to establish connection to the database. By setting TCP.VALIDNODE_CHECKING to “YES”, you inform Oracle database to allow/deny connections to the listed nodes. You may list the invited nodes using TCP.INVITED_NODES parameter in sqlnet.ora file or, alternatively, you may use the TCP.EXCLUDED_NODES parameter to disallow database connections from the listed nodes. Hope you find this information helpful!!!