As with all product upgrades, you should test to verify that existing applications work as expected with the upgrade before applying it to production systems. Adopting a proactive installation and upgrade strategy is the most effective way you can avoid rollbacks. If you first upgrade a test system with a configuration identical to the production system, you can identify potential issues and avoid the hurdles associated with a rollback. To ensure a successful upgrade, identify issues with an MDAC upgrade before committing it to production systems, and alert Microsoft Product Support Services (PSS) to any problems as early as possible in your development and deployment cycle.

As with any system upgrade, if you are unable to implement it on a test system, you should have a comprehensive backup or disk image of your production system as well as a complete recovery plan.

You can check the version numbers on specific .dll files associated with MDAC to determine the version installed on your system. The following table summarizes what file versions correspond to which MDAC versions.

Note these version numbers and compare them after an application installation to determine whether MDAC was upgraded. We also encourage you to view the MDAC Release Manifest for more information about MDAC versioning.

The Microsoft Data Access Components are system components, and installing MDAC should be considered similar to a system upgrade. You cannot remove MDAC without replacing operating system files that were upgraded by the MDAC installer. Many applications, including Microsoft Internet Explorer, Visual Studio, SQL Server, and Office require MDAC for data binding and other application functions. Removing MDAC will negatively impact or break these applications. However, under certain circumstances, Microsoft Product Support Services can assist you in solving installation and behavior problems. For more information, see "What should I do if an MDAC upgrade breaks my application?"

If you encounter issues with your application after an MDAC upgrade, consider the following:

1. Issues with components other than MDAC can be misinterpreted as being specific to MDAC. Before reporting an issue, we strongly recommend that you isolate the issue as specific to MDAC. Microsoft Product Support Services can assist in determining whether an issue is specific to MDAC.
2. If you have isolated the issue as specific to MDAC, we encourage you to contact PSS and let us work with you to develop a fix for the problem that will enable you to maintain your current installation. Many applications include updated versions of MDAC. These applications can be negatively impacted or broken if an earlier version of MDAC replaces the version bundled with the product. Rolling MDAC 2.1 back to MDAC 2.0, for example, will break Microsoft SQL Server 7 and also eliminate the Year 2000 remediation addressed in the version 2.1 release. If you discover an issue with an MDAC release, alerting us will enable the MDAC team to address the issue and continue to make MDAC a better product.
3. PSS can help you identify the source of the issue, recommend a quick-fix engineering (QFE) solution, or promote the issue as a potential QFE candidate (if applicable). Finally, under certain circumstances, PSS can assist you in removing and reinstalling MDAC after exhausting other means of resolution.

If you need to roll back to a previous version of MDAC, you have two primary options, which generally correspond to the type of system involved (test or production):

• On production systems, use your backup or disk image (taken immediately before the upgrade) to return to the configuration before the upgrade was installed.

   

• On test systems, the simplest solution is often to reformat the hard drive and reinstall all applications.

In both situations, however, we urge you to work with Microsoft Product Support Services to develop a solution that installs and maintains the upgrade version of MDAC. PSS might already have a quick-fix engineering solution that addresses your particular issue.

Under certain circumstances, PSS can assist you in removing and reinstalling MDAC after exhausting other means of resolution.

We cannot test all possible rollback scenarios. Different applications rely on specific MDAC components, and interdependencies are highly specific to individual system configurations.