NT Networking & CA-Clipper™

The Windows® NT-based Operating System family have some annoying stability issues when dealing with a legacy shared file DBMS such as CA-Clipper™. This page describes those annoyances & has solutions packaged as simple to use .REG (registry) files. Although the links below often only refer to very early versions of NT server, all the comments apply to the entire lineage up to & including Server 2003.

The basic problem is that the network redirection layer is too "lazy" in its default configuration when it comes to writing back data changes immediately to the underlying server file system. Whilst this approach does confer some speed benefits, it also introduces undesirable side-effects. These side-effects often manifest themselves as "index corruption detected" error messages in the Clipper application or (more insidiously) "lost" data during file updates. See here for details.

Other problems can be "disappearing" network drives (DOS error 55) and the dbUSE() function failing with "file is already in use" - see here and here for details.

Deletion of a closed, but recently open, file can also silently fail (the deletion appears to work, but the file still exists on the server). See here for details.

WARNING - Using the Registry Editor incorrectly can cause serious, system- wide problems that may require you to reinstall Windows to correct them. Use these tools at your own risk.

Below are two .REG files which can be used to change the behaviour of the network redirector on NT-based servers & workstations to allow Clipper applications to work more reliably. To import the changes into the registry, simply download & then double-click on the appropriate file to import into the registry. Note that you will need to ensure that you have the correct privileges (usually Administrator or equivalent) in order to import the .REG files. After the obligatory reboot, the new settings will become active.

WARNING - Clicking on the .reg links below may attempt to apply the changes to your registry directly, so please right-click & use the "Save target as..." option in your browser.

*NEW*

28 Dec 2004 - Added additional keys & comments to the files. An extra registry key was discovered which affects Windows 2000 onwards (it will be ignored on NT 4). It is recommended that the new files are applied to installations which utilized the earlier versions.

18 Oct 2006 - Jean Mathieu of Outillage Placide Mathieu inc spotted an extra 'd' on the end of "EnableOpLockForceClose" in NtWrkStn.reg - Now fixed.

NTWrkStn.reg - Registry modifications for NT-based workstations.

NTServer.reg - Registry modifications for NT-based servers (or workstations acting as servers).

Note: These modifications apply equally for Windows® NT 4, Windows® 2000/2003 & Windows® XP

Additional Clipper help is available from DaveP's Clipper FAQ and VFAQ

Klas Engwall has a useful free library for working with Clipper & Microsoft Networks here

For useful advice on Samba configuration issues on Linux, see here