Today, I am going with a fellow to monthly check the DB. An error found in alert log many times, "Inbound connection timed out (ORA-3136)". I think it's good to know what will cause this problem, so googling for a while.
Found this post in eygle site: http://www.eygle.com/archives/2006/07/sqlnet_inbound_connect_timeout.html
SQLNET.INBOUND_CONNECT_TIMEOUT Purpose Use
the SQLNET.INBOUND_CONNECT_TIMEOUT parameter to specify the time, in
seconds, for a client to connect with the database server and provide
the necessary authentication information.
If the client fails to establish a connection and complete
authentication in the time specified, then the database server
terminates the connection. In addition, the database server logs the IP
address of the client and an ORA-12170: TNS:Connect timeout occurred
error message to the sqlnet.log file. The client receives either an
ORA-12547: TNS:lost contact or an ORA-12637: Packet receive failed error
message.
Without this parameter, a client connection to the database server
can stay open indefinitely without authentication. Connections without
authentication can introduce possible denial-of-service attacks, whereby
malicious clients attempt to flood database servers with connect
requests that consume resources.
To protect both the database server and the listener, Oracle
Corporation recommends setting this parameter in combination with the
INBOUND_CONNECT_TIMEOUT_listener_name parameter in the listener.ora
file. When specifying values for these parameters, consider the
following recommendations:
Set both parameters to an initial low value. Set the value of the
INBOUND_CONNECT_TIMEOUT_listener_name parameter to a lower value than
the SQLNET.INBOUND_CONNECT_TIMEOUT parameter. For example, you can
set INBOUND_CONNECT_TIMEOUT_listener_name to 2 seconds and
INBOUND_CONNECT_TIMEOUT parameter to 3 seconds. If clients are unable to
complete connections within the specified time due to system or network
delays that are normal for the particular environment, then increment
the time as needed.
See Also: Oracle9i Net Services Administrator's Guide for information about configuring these parameters
Default None
Example SQLNET.INBOUND_CONNECT_TIMEOUT=3
Very important to know that, it's about db security.
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