WARNING: inbound connection timed out (ORA-3136) The " WARNING: inbound connection timed out (ORA-3136) " in the alert log indicates that the client was not able to complete it's authentication within the period of time specified by parameter SQLNET.INBOUND_CONNECT_TIMEOUT. You may also witness ORA-12170 without timeout error on the database server sqlnet.log file. This entry would also have the client address which failed to get authenticated. Some applications or JDBC thin driver applications may not have these details. From 10.2 onwards the default value of this parameter is 60 seconds , hence if the client is not able authenticate within 60 secs, the warning would appear in the alert log and the client connection will be terminated. This timeout restriction was introduced to combat Denial of Service (DoS) attack whereby malicious clients attempt to flood database servers with connect requests that consumes resources. Cause: There can be three main reasons for this ...