Enabling or disabling critical mode in Lync Server 2013 to block or allow IM and web conferencing sessions if Archiving fails

Lync has the ability to allow Administrators to turn enable “critical mode” when Lync Archiving is enabled.   When critical mode is enabled in the Lync environment, this gives administrators the peace of mind that for any reason the backend database “LCSlog” that is created for Lync Archiving is not available for any reason then no Instant Messaging and / or Web Conferencing will be allowed to take place in the Lync environment until the data can be archived once again. We will take a look at how to enable criticality mode within Lync and what happens once enabled and your archiving database is not available.

Enabling Critical Mode

1. From a user account that is assigned to the CsArchivingAdministrator or CsAdministrator role, log on to any computer in your internal deployment.
2. Open a browser window, and then enter the Admin URL to open the Lync Server Control Panel. For details about the different methods you can use to start Lync Server Control Panel, see Open Lync Server 2013 administrative tools.
3. In the left navigation bar, click Monitoring and Archiving, and then click Archiving Configuration.
4. Click the name of the appropriate global, site, or pool configuration in the list of archiving configurations, click Edit, click Show details, and then do the following:
5. To set how archiving behaves when a failure occurs, select or clear the Block instant messaging (IM) or web conferencing sessions if archiving fails check box.
6. Click Commit.

Enable/Disable Critical Mode from PowerShell

Set-CsArchivingConfiguration -Identity "site:" -BlockOnArchiveFailure $True

Set-CsArchivingConfiguration -Identity "site:" -BlockOnArchiveFailure $False

What happens when critical mode is activated?

By enabling critical mode in the Lync environment we have stated that we don’t want IM’s to traverses the environment without being captured in the archiving database.  In addition we state by enabling critical mode that conferencing functionality is blocked as well until the archiving database is available and files can once again be copied to the archiving file store.  So the question is now; “What happens when the SQL database that is used for archiving is no longer available?”  Since we’ve enabled critical mode, the feature blocks users from instant messaging or conferencing across the Lync environment.

Now before Lync 2010, what would happen is the Lync Front End core service would stop and as a result would stop all Lync modalities (IM, Enterprise Voice, and Conferencing) traffic across the Front End servers which would be detrimental to Lync.  The good thing is that is not the case anymore. The voice piece of Lync will continue to be operational in the event the Lync pool back-end SQL database is not available for any reason.  The other key modalities IM and Conferencing wouldn’t be functional to the user community until the archiving back-end database becomes available again.