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ORA-12537: TNS: Connection Closed Error

Oracle’s ability to be customized with deep mechanics in regards to the construction of company databases is one of many reasons that it has become so prevalent in corporations today. Due in part to the complex nature of Oracle database structures, occasionally errors can arise, some of which carry a string of causes and additional problems. The ORA-12537 connection closed error is an example of one of these types of issues that is associated with an assortment of causes and potential outcomes. Let us look at some of these initial triggers for the error and see what can be done to counter them so databases can be returned to full functionality.

The Problem

The ORA-12537 is defined as an informational error, a message error triggered alongside a secondary error that typically offers the true programming issue. Oracle docs describes the cause as “a normal end-of-file condition being reached; partner has been disconnected”. It can occasionally relate to configuration issues in the sqlnet.ora, listerner.ora files or the protocol.ora. Furthermore, the error can derive from the firewall in a network being disconnected due to idling connections.

Another potential cause is that a path name is too long for the Oracle TNS client. Just as well, there is a common bug in Oracle known as 1566794: CONNECTIONS FAIL WITH ORA-12537 WHEN USE_SHARED_SOCKET IS SET IN 8.1.7. The resolution to this condition is to set the USED_SHARED_SOCKET parameter to FALSE.

The error can also occur if the user has listed a 10g database SID with a 9i listener, which can create the problem because of invalid inter-version connections. Additionally, the user can generate an ORA-12537 error in Oracle Apps 11i due to an eBusiness Suite security feature.

One final cause of the error is when the Tnsping Net Service name fails with the TNS-12537. This occurs because the Sqlnet.ora file parameter TCP.VALIDNODE_CHECKING is enabled and TCP.INVITEDNODES is set to a specific IP’s of the client machine. These parameters are enable by default in the Oracle Apps Installation.
The Solution

An initial step for taking on this error is to of course check your records and see what events transpired just prior to the occurrence of the event. From there, the user should attempt to verify that all service names match between the listener and the remote client connect strings. In the event that the firewall was disconnected to due idleness, check the idling parameters across your system and adjust them to reflect the networks usage.

For a path name that is too large, install the exe in a shorter named directory. The user can also modify the TNS Names entry so that it is a bit shorter, they can remove parameters from the entry that are largely unnecessary and they could replace domain names with IP addresses in the event that they shorten things up. When the error is prompted by the aforementioned eBusiness Suite security feature, the solution is to edit your sqlnet.ora file to include the client IP address in the tcp.invited_nodes = (hostname, etc.).

Lastly, to correct the TNSping Net Service name fails error, the user can disable these parameters in the Sqlnet.ora. The user can also add the client machine’s IP address in the TCP.INVITEDNODES list.
Looking forward

As can be seen from above, there are numerous causes of the ORA-12537. With that said, the user can make a couple of adjustments to offset this error. Maintaining an awareness of parameters that are enabled and noting idle times across the network can go a long way in preventing not just this error, but a number of problems within Oracle. Another slight modification to be made is keeping the programming as neat and concise as possible. Working to eliminate long strings of domain names and code is a strong discipline to instill in the database programming process. For more information about these methods, it would is advised to speak with a licensed Oracle consultant.