When you specify a constant for a CHARACTER or VARCHAR data type without the UPPERCASE option, a data value must match the case of the constant to be compressed.
For example, if a column named Doc_Type is defined as follows:
Doc_Type CHARACTER(6) COMPRESS 'Manual'
then each value must be entered as ' Manual ' in order to be compressed. A value in a different case, such as ' MANUAL ' or ' manual,' is not compressed.