char_length() returns -1

Hi. I cannot find it documented anywhere what it means when the function char_length() returns -1 . We are working with IDS version 9.4 FC5 (on a Tru64 system). I have a table called page_facts with the following columns integer page_id, lvarchar title(500) CLIENT_LOCALE and DB_LOCALE are both set to "en_us.utf8" if I run the following query: select * from page_facts where char_length(title) = -1 I get several records returned. I have searched high and low for what that "-1" means - I'm assuming it means that there is malformed utf-8 in the title column. In fact I saw one posting to this group where somebody put a check constraint on a table that checked that the char_length() of a varchar column was greater than 0. But I don't see it documented anywhere what "-1" actually means. BTW - is putting a constraint like that on my tables a good idea? What would be the performance impact if the lvarchar column had a maximum size of 25000 bytes (as one of my tables does). Thank you advance, Lou