In the Tableau Data Source tab, if you drag and drop a OBIEE fact table with millions of rows into the join area and press "Update Now" or "Automatically Update", then the performance will be very slow. In addition, you might also see the following error message:
Solution:
As a best practice, we recommend that you do not select "Update Now" or "Automatically Update" in the Tableau Data Source tab. Instead, just drag and drop the tables into the join area in Data Source tab, let BI Connector and Tableau automatically join the tables. Then, go to Worksheet tab. Uncheck "Auto Update Worksheet". Create your worksheet with columns, rows, measures and filters and then finally update the worksheet to see the chart.
The reason that we recommend not to select "Update Now" or "Automatically Update" is simple. Tableau is an in-memory application. When you drag and drop a fact table into the join area and press Update Now, Tableau will send a “Select * from Facts_Table” to OBIEE and query all the data in that table. This is not a typical query that you would run in OBIEE since you will be fetching millions of records in the Fact table and consequently you will see slow performance and/or the data source connection/timeout error. Therefore, Do not select Update Now or Automatically Update in Tableau. For the same reason, do not select "Auto Update Worksheet" in the Worksheets tab.
Step by step instructions for improving performance and avoiding data source connection error
1. Drag and Drop the fact table, and necessary dimension tables into the join area. They will automatically be joined by Tableau and BI Connector.
2. Do not press “Update Now” or “Automatically Update”.
3. Go to Worksheet. Uncheck “Auto Update Worksheet."
4. Drag and drop the dimension, measures into the Tableau Rows and Columns as appropriate.
5. Set the Filter conditions on dimensions as appropriate.
6. Execute the worksheet (by clicking on the Update button). You will see the data refreshed in the worksheet now.