HP CIFS Opportunistic Locking Usage Guidelines

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Chapter 1 Introduction
CIFS/9000 Server on HP-UX manages file access among Windows clients with Windows style
file locking. It applies a very effective set of file locking features that are managed by the
user-space client processes on the server, and provides excellent data security and integrity
in a multi-user environment. CIFS/9000 Server also integrates some Windows locking
protocols with the underlying HP-UX operating system locking pr otocols, and therefore
provides some interoperability with UNIX and NFS style file locking. For a detailed
discussion of CIFS/9000 Server file locking, read the “CIFS/9000 Server File Locking
Interoperability” whitepaper at:
http://snsl.cup.hp.com/page.php?id=26
Further file locking enhancements are currently under development in the HP CIFS/9000 lab
with the implementation of the CIFS/9000 Extended File System, which is a custom designed
virtual file system (VFS) layer for HP-UX.
Opportunistic Locking is a unique Windows file locking feature. It is not really file locking,
but is included in most discussions of Windows file locking, so is considered a defacto locking
feature. Opportunistic Locking is actually part of the Windows client file caching
mechanism. It is not a particularly robust or reliable feature when implemented on the
variety of customized networks that exist in enterprise computing, but can be effective in
providing modest perceived performance optimization.
Like Windows, CIFS/9000 Server implements Opportunistic Locking as a server -side
component of the client caching mechanism. Because of the lightweight nature of the
Windows feature design, effective configuration of Opportunistic Locking requires a good
understanding of its limitations, and then applying that understanding when configuring
data access for each particular customized network and client usage state.