When a table is created with the DATE data type, a two-byte FP index is created on the DATE field, which is independent of the settings in database option MINIMIZE_STORAGE.
If you want to create a three-byte FP or flat-style FP index on the DATE field, use the following IQ UNIQUE values when creating the table:
For a three-byte FP — IQ UNIQUE should be between 65537 and 16777216.
For flat-style FP — IQ UNIQUE should be higher than 16777216.