HP CIFS Opportunistic Locking Usage Guidelines

4.3 Unix or NFS Client Accessed Files

Local HP-UX (Unix) and NFS clients access files without a mandatory file locking

mechanism (see the whitepaper “CIFS/9000 File Locking Interoperation” at

http://snslweb.cup.hp.com/getfile.php?id=58). Thus, these client platforms are incapable of

initiating an oplock break request from the server to a Windows client that has a file cached.

Local HP-UX or NFS file access can therefore write to a file that has been cached by a

Windows client, which exposes the file to likely data corruption.

If files are shared between Windows clients, and either local HP-UX (Unix) or NFS users,

then turn opportunistic locking off.

4.4 Slow and/or Unreliable Networks

The biggest potential performance improvement for opportunistic locking occurs when the

client-side caching of reads and writes delivers the most differential over sending those reads

and writes over the wire. This is most likely to occur when the network is extremely slow,

congested, or distributed (as in a WAN). However, network latency also has a very high

impact on the reliability of the oplock break mechanism, and thus increases the likelihood of

encountering oplock problems that more than offset the potential perceived performance

gain. Of course, if an oplock break never has to be sent, then this is the most advantageous

scenario to utilize opportunistic locking.

If the network is slow, unreliable, or a WAN, then do not configure opportunistic lock if there

is any chance of multiple users regularly opening the same file.

4.5 Multi-User Databases

Multi-user databases clearly pose a risk due to their very nature – they are typically heavily

accessed by numerous users at random intervals. Placing a multi-user database on a share

with opportunistic locking enabled will likely result in a locking management bottleneck on

the CIFS/9000 Server. Whether the database application is developed in-house or a product

such as Microsoft Access, ensure that the share has opportunistic locking disabled.

4.6 PDM Data Shares

Process Data Management (PDM) applications such as IMAN, Enovia, and Clearcase, are

increasing in usage with Windows client platforms, and therefore SMB data stores. PDM

applications manage multi-user environments for critical data security and access. The

typical PDM environment is usually associated with sophisticated client design applications

that will load data locally as demanded. In addition, the PDM application will usually

monitor the data-state of each client. In this case, client-side data caching is best left to the

local application and PDM server to negotiate and maintain. It is appropriate to eliminate

the client OS from any caching tasks, and the server from any oplock management, by

disabling opportunistic locking on the share.

4.7 Force User

CIFS/9000 Server includes an smb.conf parameter called “force user” that changes the user

accessing a share from the incoming user to whatever user is defined by the smb.conf

variable. If opportunistic locking is enabled on a share, the change in user access causes an

oplock break to be sent to the client, even if the user has not explicitly loaded a file. In cases