I love the Characteristic Relationships as they help and
automate the validation and data entry stuff.. here is another piece of gem from the SAP HELP!!
following advantages result from data entry in manual planning:
In a planning layout for which the option "All
Possible Characteristic Combinations" was selected, the Cartesian product is not (as in earlier releases with the option
"form-based") formed of all theoretically possible combinations of characteristic values, but instead only those combinations
that were defined as sensible in the defined characteristic relationship. For example, in a lead column that contains the
characteristics cost center and currency only the valid currency for this is offered for data entry for every cost center
(and not all currencies contained in the package selection) As a result, data entry is made much easier since only the really
relevant value combinations are offered. In addition, such planning layouts are now much more compact and clearer and this
leads to better answer times of the system.