Many providers generate the values of XXX_UNIQUE_NAME columns from concatenating several names. For instance, the unique name of a level may be <dim_name>.<hier_name>.<level_name>. In such a case, the provider may not be able to report the maximum sizes of such columns (when methods on the IColumnsInfo interface are called to determine a size). If they are unable to determine the maximum size, providers return a size of ~0 (all the bits are set to 1) to indicate that they are unable to accurately determine it.