UNLOCK is used to set an open databank editable.
UNLOCK databank ;
This opens up mybank in the last position on the databank list (F2), and sets it editable (so that data inside can be changed).
You may use OPEN<edit> to open an editable databank in the first position. OPEN<edit>mybank; is actually short for OPEN<first>mybank; UNLOCK mybank;.