This was covered in an ancient book from IBM. From the 70's if not the 60's. Basically it was saying the first screen should do a read for input only so it wouldn't do a lock. Then after the interactive changes it should read the file again, this time with the lock. If nothing has changed since the last read then it should do the update with the new values. If stuff has changed, like from another interactive user, then you will have to decide on how to handle that.
A "deadly embrace" was when USERA locked a record like this, let's say CUSTA. Then USERB locks a record like this, lets say CUSTB. Now if USERA tries to read CUSTB without updating CUSTA (F12 perhaps) it doesn't release the record of CUSTA and waits on CUSTB. If USERB does the same thing by switching to CUSTA then they are both waiting perpetually for the other to unlock their rows.
Rob Berendt
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