The possible root cause for errors during extract is errors in RPD for one or more columns in the selected tables/folders in OBIEE.  To resolve this error, 

  1. You should remove unwanted columns by using Hide Unused Columns in Tableau.  This is because Tableau would Select * from all the tables included in the data source.  e.g., Select * from Table A, Table B, Table C.   This might error out in OBIEE if your OBIEE RPD has errors in one of the columns in the selected tables.  OBIEE RPD could have errors such as "missing physical mapping" for some columns which are not used.  But since Tableau is querying on all the columns in a Table/Folder, the query will fail in OBIEE.   So, you should choose only a small number of columns for your query and hide the unwanted columns.  Then Tableau will query only the required columns in the table.     
  2. You should use filters to limit the amount of data coming into Tableau from OBIEE because OBIEE administrators might have set limits on the number of rows (e.g., 200,000) that can be queried.  OBIEE might error out if you are trying to extract a large number of rows beyond that limit.  

If you have tried and eliminated both these root causes for the error, please send us a clean set of log files for the error to support at biconnector dot com.  Please refer to the below article for log file generation:

How to generate a clean set of BI Connector log files for troubleshooting?