Another topic could be added in the goodbook of Best Practice .In the OBIEE hierarchy, starting from the top and moving down. At each level below the Grand Total level, double-click the level. In the field Number of elements at this level: enter 10 and increase in increments of 10 through all levels in the hierarchy. This is necessary to avoid the below Hierarchy errors and let BI server optimizes the aggregated query :
[nQSError: 15001] Could not load navigation space for subject area Student Enrollment.
[nQSError: 15019] Table <Logical table name> is functionally dependent upon level <Logical level>, but a more detailed child level has associated columns from that same table or a more detailed table.
This message occurs when either a key is defined under the Total level or when the first child level below the Total level contains two keys. Right-click on the Total level and select Properties. The Keys tab should be grayed out. If it is selectable, check to see what is there and delete it. Go to the next level down, right-click, select the Keys tab. Only one Key should appear. Delete the key that does not belong.