You may want to check for an updated documentation regarding file and record locking issues on the Microsoft Support web site. Additionally, search for the word locking on the Samba web site.

Section of the Microsoft MSDN Library on opportunistic locking:

Microsoft Knowledge Base, “Maintaining Transactional Integrity with OPLOCKS”, Microsoft Corporation, April 1999, Microsoft KB Article 224992.

Microsoft Knowledge Base, “Configuring Opportunistic Locking in Windows 2000”, Microsoft Corporation, April 2001 Microsoft KB Article 296264.

Microsoft Knowledge Base, “PC Ext: Explanation of Opportunistic Locking on Windows NT”, Microsoft Corporation, April 1995 Microsoft KB Article 129202.