Microsoft Windows Networks

Improperly configured Windows networks can lead to data corruption in any file system database, including the SherWare database. Two Windows networking behaviors, opportunistic locking (on Windows servers) and read caching (on Windows clients) are sources for corruption potential. This paper is provided for SherWare customers to discuss these behaviors, their effects and what can be done to minimize the chances of data corruption on Windows networks when running Accounting Manager oir Disbursement and JIB Manager applications, and to centralize this information in one convenient place.

A detailed explanation of this is provided at: http://support.sherware.com/smb2.html
Below is listed just a few points from the link.

SherWare Recommendations

The database is an ISAM database and thus susceptible to the effects of the default Windows oplocks settings. Using the SherWare database on Windows networks without disabling oplocks is not recommended or supported and has a high likelihood of data corruption.

Reliable database operation on Windows Networks can be achieved using the SherWare database, provided that the network is properly configured. You can use the information in this paper to set up your Windows network's oplocks parameters. One downside to using this method are maintenance issues: you must continually ensure that each and every server and client using an application accessing the SherWare database has oplocks disabled and are always maintained in that state.

One method to ensure that oplocks are disabled on client PCs is to add code to applications that checks those settings on application startup. The folks at VDF-Guidance.com have created an open source project named RegCheck for this purpose.

Disabling oplocks may have a performance impact on Windows networks.

What Operating Systems are Affected?

All computers running Windows operating systems that host or access DBF database tables accessed by other Windows PCs need to have oplocks disabled in order to minimize the chances of database corruption.

Oplocks can be disabled on either (or both) of these:

the client side (a Windows PC that accesses an DBF database table hosted on another PC)
the server side (a Windows PC that hosts an DBF database table accessed from another PC)
The Windows operating system list that we currently support for our products includes Windows 2000, Windows XP, Windows Vista, Windows 7, Windows Server 2003 and Windows Server 2008.

What Environments Are Not Affected?

There are some environments and scenarios that we support that may not be affected by oplocks, even if using the SherWare database:

Local database access
In general, whenever an SherWare database table is accessed on the same PC where that table is located, oplocks do not apply.
Windows Terminal Services and Citrix
Under normal use for these environments, users log onto a Windows server and run applications locally on that server. If, however, an SherWare database is located on another server than the one running WTS/Citrix, oplocks between the WTS/Citrix server and the database server must be disabled.
Web Application Server Applications/Web Services
In web applications users access a web browser which requests data from a web application and/or data is requested via a web service. In both cases, the web application on a web server accesses the database, the client does not. If the data is located on the same server, oplocks do not come into play. If, however, an SherWare database is located on another server than the one running the web application, oplocks between the web server and the database server must be disabled.