Resolution:
In TIBCO BusinessWorks ProcessMonitor (BWPM) we have to set the Connection Pool Size under the JDBC settings (Administration>Connections>JDBC) to ensure enough connections are available in the connection pool and avoid the error, "Error pool empty. Unable to fetch a connection in 30 seconds".

The connection pool is used both for writing and reading data from the database. It is recommended to set this value as per a rule of thumb. With BWPM 3.0.0.x and previous versions, the value for the connection pool should be <number of data provider threads> + 5 * < average amount of concurrent GUI users> + 10. In BWPM version 3.0.1, the value for the connection pool size should be set to 1.5 * <number of data provider threads> . GUI connections will not be considered while setting the connection pool size.