For organizations that have archiving or compliance needs, Lync Server provides the Archiving Server role, which can capture IM traffic. All archiving data is saved to a Microsoft SQL Server database and is separate from the database used for all user services and contact lists.
Archiving can be enabled at the pool level to capture traffic for all users or it can be enabled on a per-user basis if archiving needs to done for only a select group of users. If an organization has no need to capture internal traffic, archiving can also be configured to log only federated traffic.
In the event of an archiving server failure, the administrator has the option to shut down the pool and user services to ensure the organization meets compliance regulations.