Users Guide

Installing Managed System Software on Microsoft Windows Operating Systems 71
System Recovery on Failed Installation
The Microsoft Software Installer (MSI) provides the ability to return a system
to its fully working condition after a failed installation. MSI does this by
maintaining an undo operation for every Standard Action it performs during
an install, upgrade, or uninstall. This operation includes restoration of deleted
or overwritten files, registry keys, and other resources. Windows temporarily
saves any files that it deletes or overwrites during the course of an installation
or removal, so they can be restored if necessary, which is a type of rollback.
After a successful installation finishes, Windows deletes all of the temporary
backup files.
In addition to the rollback of MSI Standard Actions, the Dell OpenManage
library also has the ability to undo commands listed in the INI file for each
application if a rollback occurs. All files that are modified by the Dell
OpenManage installation actions are restored to their original state if
a rollback occurs.
When the MSI engine is going through the installation sequence, it ignores
all actions that are scheduled as rollback actions. If a Custom Action,
MSI Standard Action, or a Dell OpenManage installation action fails, then a
rollback starts.
An installation cannot be rolled back once it is completed; transacted
installation is only intended as a safety net that protects the system during
an installation session. If you want to remove an installed application,
for instance, you should simply uninstall that application.
NOTE: Driver installation and removal is not executed as part of the installation
transaction and therefore cannot be rolled back if a fatal error occurs during
execution.
NOTE: Installations, uninstallations, and upgrades that you cancel during installer
cleanup, or after the installation transaction is completed, are not rolled back.