Wednesday, May 11, 2011

Deffered Custom Actions

Deferred Execution Custom Actions:
Deferred custom action's purpose is to delay the execution of a system change to the time when the installation script is executed. This differs from a regular custom action, or a standard action, in which the installer executes the action immediately upon encountering it in a sequence table or in a call to MsiDoAction.

The installer does not execute a deferred execution custom action at the time the installation sequence is processed. Instead the installer writes the custom action into the installation script. The only mode parameter the installer sets in this case is MSIRUNMODE_SCHEDULED. See MsiGetMode for a description of the run mode parameters.

A deferred execution custom action must be scheduled in the execute sequence table within the section that performs script generation. Deferred execution custom actions must come after InstallInitialize and come before InstallFinalize in the action sequence.

Custom actions that set properties, feature states, component states, or target directories, or that schedule system operations by inserting rows into sequence tables, can in many cases use immediate execution safely. However, custom actions that change the system directly, or call another system service, must be deferred to the time when the installation script is executed.

Because the installation script can be executed outside of the installation session in which it was written, the session may no longer exist during execution of the installation script. This means that the original session handle and property data set during the installation sequence is not available to a deferred execution custom action.

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