public int fd() throws DbException;
The Db.fd method returns a file descriptor representative of the underlying database. This method does not fit well into the Java framework and may be removed in subsequent releases.
The Db.fd method throws an exception that encapsulates a non-zero error value on failure.
The Db.fd method may fail and throw an exception for errors specified for other Berkeley DB and C library or system methods. If a catastrophic error has occurred, the Db.fd method may fail and throw a DbRunRecoveryException, in which case all subsequent Berkeley DB calls will fail in the same way.
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