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ORA-12170: TNS: Connect timeout occurred tips

Oracle Database Tips by Burleson Consulting



Question: I'm getting the error "ORA-12170: TNS:Connect timeout occurred" when I try to connect to my database via OEM.  How do I resolve the "ORA-12170: TNS: Connect timeout occurred" error?


Answer: The ORA-12170 error can be for many reasons, firewall issue, database down, listener down, bad sqlnet.ora parm, network trouble, etc.  The docs note:

ORA-12170: TNS:Connect timeout occurred

Cause: The server shut down because connection establishment or communication with a client failed to complete within the allotted time interval. This may be a result of network or system delays; or this may indicate that a malicious client is trying to cause a Denial of Service attack on the server.

Action: If the error occurred because of a slow network or system, reconfigure one or all of the parameters SQLNET.INBOUND_CONNECT_TIMEOUT, SQLNET.SEND_TIMEOUT, SQLNET.RECV_TIMEOUT in sqlnet.ora to larger values. If a malicious client is suspected, use the address in sqlnet.log to identify the source and restrict access. Note that logged addresses may not be reliable as they can be forged (e.g. in TCP/IP).

Your sqlnet.ora file can be found in your $ORACLE_HOME/network/admin directory.


ORA-12170 and hosts file


Verify that your /etc/hosts file has a DNS entry:  diogenes

In Windows XP, make your hosts file is located at win/system32/driver/etc/ and on UNIX, Linux, check /etc/hosts.

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Note: This Oracle documentation was created as a support and Oracle training reference for use by our DBA performance tuning consulting professionals.  Feel free to ask questions on our Oracle forum.

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Errata?  Oracle technology is changing and we strive to update our BC Oracle support information.  If you find an error or have a suggestion for improving our content, we would appreciate your feedback.  Just  e-mail:  and include the URL for the page.


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