Windows has its own locking mechanism, called Opportunistic Locking, for files shared in a network environment. This mechanism is enabled by default and can contribute to file errors and performance issues in such an environment.
Disable Windows Opportunistic Locking.
There is a Microsoft KB article regarding Opportunistic Locking here:
Note that there are two separate registry keys; one controls the granting of locks and the other controls the requesting of locks. On each machine both registry keys should be set to disabled. Set OplocksDisabled to 1 and set EnableOplocks to 0.
Attached is a zip file containing an AcuCOBOL-GT program that will make the registry entries to disable Windows Opportunistic Locking. This program is provided without warranty. Since the program modifies the Windows registry a backup of the registry should be made before running it.
NOTE: The winreg program also sets the method for opening files to "fast mode". If the default "safe mode" is desired then execute the program with the included runtime configuration file, safe.cfg.
Read more about safe/fast modes in KB article 25085.