Introduction

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However, occasionally, a small number of users will be inconvenienced by being forcibly logged out. When this happens, the user is forced to log back in unexpectedly.  If you care to know why this happens, please read the remainder of this page.

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At all times, at least one server is available for new sessions, giving the appearance that the system has never shut down.  As users log out of the previous version, they will be automatically connected to the new version.

Long Running Sessions

In practice, it often takes four to eight hours to complete a rolling upgrade.  This is because a few users keep an active session for the entire business day.  A single user can prevent the upgrade from proceeding by keeping a single session active. For most upgrades, this is not an issue so the sessions are allowed to expire normally.  However, for an important upgrade or bug fix, the SSDT may decide to speed up the process by forcibly terminating a few users.   Whenever possible, we only terminate sessions that have been inactive for at least 15 minutes but occasionally are forced to terminate more active users. 

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