Disscoverer Join configuration error problem

Question

Hi i am opening a discoverer report by logging through user A and get the following error
Error
Unable to open the worksheet requested.
- OracleBI Discoverer was unable to find the worksheet that was requested.
- BIB-10310 An unknown exception occurred.
- Join configuration cannot be resolved. Reason: the joins on the detail folders use different keys to join to the master Attempt to open workbook failed.
But when i login through User B , i am able to see the report .
I have given user A access to underlying tables, business areas . Still i have the problem .
and it is high priority for me to solve the issue

Answer 1

Hi
The fan trap occurs when you have two or more 1 to many relationships at the same time from the same folder. What you will end up with is a cartesian join where the values are multiplied by the number of rows found in the other table. Here's a simple example:
Let's say we have 3 folders, one called Department, one called Dept Expense, and one called Dept Budget. The model says that for any given department there can be many expenses, and for any given department there can be many budget items. If you attempt to pull all of the detail values for expenses and all of the detail values for budget for a given department you will have a fan trap. So if there are 2 expense items and 5 budget items the expense rows will be multiplied by 5 and the budget rows will be multiplied by 2 giving 10 rows of data. Attempting to build this kind of query would give the wrong answer and this is what Discoverer's fan trap protection blocks. When enabled it will not allow the query to run with detail values on both sides. When disabled it will display the rows by rewriting the query into one or more sub-queries but Discoverer will still not let you compute totals for all of the columns which are part of a cartesian join. Many users think that Discoverer has broken at this point and export the data to Excel and add it up there completely oblivious to the fact that they have duplicate rows and that the totals will be completely wrong.
It is very, very dangerous to export data to Excel when Discoverer is not computing a value.* You have to understand why Discoverer does not compute and go from there.
It can be enabled/disabled at the user level in the Plus tool by using Tools | Options | Advanced from the menu bar. Please be aware that disabling is a global function and applies to ALL queries run from that point. It is generally a bad idea to disable the fan trap protection.* The right solution is to rectify the muliple one to many relationships, perhaps by creating a database view instead using denormalization techniques.
Best wishes
Michael