how can i free attachment field in database

[Lynne]

You moved the attachments from the database to the file system and all is working just fine now (right?) but you are wanting to make the attachment table smaller after the move (did you make the move in order to make the database smaller?)?

After the move, did you run Optimize on the attachment table? That will make the size smaller. (admin cp > maintenance > repair/optimize tables > select attachment > Continue)