I need to alter a field definition from varchar(400) to dm_memo. Can I
just run this:

update RDB$RELATION_FIELDS set
RDB$FIELD_SOURCE = 'DM_MEMO',
RDB$COLLATION_ID = -1
where (RDB$FIELD_NAME = 'DESCRIPTION') and
(RDB$RELATION_NAME = 'ACTIONLOG')

or do I need to create a new field, assign it, drop the old field....

Thanks
Ed Dressel