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For Unix check the /etc/resolv.conf configuration file if entries for name servers and host name resolution are correct.

Oracle® DBMS Issues

The Oracle® FAN functionality provides enhanced high availability by allowing very fast detection of failures. However, if the FAN functionality is not set up correctly then this can result in a denial of connection though the Oracle listener is accessible, e.g. by tnsping.

To check this root cause the FAN can be disabled by use of a Java option like this:

export JAVA_OPTIONS="-Doracle.jdbc.fanEnabled=false"

Other Root Causes

Another possible reason for delays could be a huge number of files in /tmp as the JDBC interface tries to list files in the /tmp directory when SecureRandom.nextBytes(byte[]) is invoked.

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