Resolution1. Create an oracle.tdc file as below
<?xml version='1.0' encoding='utf-8' ?>
<connection-customization class='oracle' enabled='true' version='8.10'>
<customization name='CAP_JDBC_USE_ADAPTIVE_FETCH_SIZE' value='no' />
2.Create oracle.properties as below.
NOTE: the user should adjust the value "10000" to suit their own environment.
3. Put oracle.properties and oracle.tdc into C:\Users\xxxx\Documents\My Tableau Repository\Datasources.
4. Put the Oracle JDBC driver (e.g. ojdbc8.jar) into C:\Program Files\Tableau\Driver.
5. Start Tableau Desktop and use Oracle connector to connect. Tableau will use JDBC to connect to Oracle and the customized Fetch Size.
6. For quicker tuning suitable Fetch Size, after connecting to Oracle in Tableau Desktop, click Data - Extract data and choose top 2000,000 rows. Then enable performance recording to check how much time elapsed for the query. (Help - Settings and performance)