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Understanding the appropriate places to use “Impact” & what “Reboot Behavior” should be set to when “Impact” is not set to Normal

by Lawrence Garvin (@LawrenceGarvin)

In Sunday’s MMS presentation I mentioned the two fields Impact and Reboot Behavior, but did not have time in that presentation to talk about these two options in a way that would do them justice.

Impact has three possible values “Normal”, “Minor”, and “Requires Exclusive Handling”. The Windows Update Agent responds to these values when used with a standalone WSUS server (or updating from WU/MU), but in a Configuration Manager environment they have much less significance because the Configuration Manager agent is controlling the updating process. However, these values are still displayed in the update metadata and can convey useful information to a patch administrator, so they should be set correctly. Almost all updates will have the setting of Impact = “Normal”.

“Minor” means that an update does not require a service restart or a system restart. This is a very strict qualification. If any possible scenario exists that could cause a system to need to restart, then the update cannot be classified as “Minor”. This has relevance to a Windows Update Agent configuration setting Allow Automatic Updates immediate installation. When this setting is enabled, and the Windows Update Agent detects an approved update with Impact=”Minor”, the WUAgent will download and install that update immediately.

“Requires Exclusive Handling” is the setting to declare an update as exclusive. An update is exclusive when it cannot be installed in the same collection of updates with another update. Typically these exclusive updates are major updates, such as Windows service packs, .NET service packs, and Internet Explorer upgrades. When the Windows Update Agent identifies as an update as exclusive, it handles it differently than other updates. Exclusive updates are deferred for installation until all other available updates are installed. If you’re approving (WSUS) or deploying (ConfigMgr) an exclusive update, be aware of other updates that may be visible to that client.

Reboot Behavior … does *NOT* control whether a client system reboots after an update is installed. This option merely imparts information to the patch administrator on what the expected behavior of the update is with respect to whether a system will, can, or won’t require a restart. The options are “Never reboots”, “Always requires reboot”, and “Can request reboot”.

“Never reboots” generally only applies to updates with Impact=”Minor”.

“Always requires reboot” typically would apply to exclusive updates and updates known to affect OS files that would be normally open/locked during the update installation.

“Can request reboot” is the option you’ll see in almost all updates.

What actually determines whether an update triggers a system restart request is the installer return code. The return code ‘3010’ is reserved for such scenarios, and most EXE-based installers will return this code if the installer has performed some action ( or been unable to perform an action) that requires a system restart. The only way to know whether an update does, or does not, require a system restart is to TEST IT.

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