When you are setting up a connection to an external data source, Spotfire needs to map the data types in the data source to data types in Spotfire.
When working with Oracle Essbase, all measures are being mapped as Real and all dimensions are mapped as String. Results from different operations in Spotfire, such as markings and evaluation of expressions, may also result in a Boolean.
See also:
Details on Oracle Essbase Connection
Using the Data Panel with Oracle Essbase Data