Locked... or not?

Hello, I wonder if anybody can help me with this locking problem. I have a customer running C2000 phase 3 which in turn uses ISAM Ver.5.0. I'm developing a 'C' routine using ISAM Ver 6.11. The situation is this: One user amending a record in file X (in C2000) A 'C' program then tries to open file X to insert a record. The 'isopen' returns error code 113 (file exclusively locked). However a second user (also in C2000) can now insert a record. My question is why can two users within C2000 insert / amend different records in the same file, but my 'isopen' returns error code 113? Thanks in advance. Gary -- | MPS, Merit House, Priory Park West, | Hessle, Hull, East Yorkshire. | HU13 9PB, ENGLAND | Tel: +44 01482 647400 | Fax: +44 01482 648864 | http://www.webalchemy.co.uk/mps | Gary.Vance@MPS.co.uk