This is why good ole whiteboards and a bunch of cow orkers are helpful. Knowing flow, seeing possible conditions, and knowing tidbits about software. Of course, using a semaphore file should solve these issues, since you take the actual locking piece away from the wanted data set. For example, if you lock a semaphore before opening the DBM, the DBM can close and reopen all it wants, since the semaphore is the lock.

Cheers,
KM