Server Side Conversation History and Exchange

Symptom:

After migrating users from Lync Server 2013 to Skype for Business 2015, we noticed High CPU and memory exhaustion and slow server performance on our Front-Ends. In some cases, IM and Presence would fail and calls could not be completed.

Root Cause:
Microsoft observed that there were an excessive number of records in the Front-End local SQL Express LyncLocal\LYSS database caused by our current client policy configuration.

We discovered that the client policies need to be configured correctly when Skype for Business Server is installed.  The server side EnableServerConversationHistory policy set to True, but should be set to FALSE since we do not yet have the Exchange Partner configuration in place. This caused performance problems and has been attributed to a Skype Server system failures we experienced during user migrations.

Also, some clients are using IM archiving, SQL method.  This client policy should be set as follows. ExchangeArchivingPolicy: UseLyncArchivingPolicy

lyss: Lync Storage Service is used to maintain HA within a FE pool. It is a blob database with abstract writes to back-end database. It maintains a copy of the data within Front End servers in the pool temporarily, and delete that data once it has been delivered to the final database server. It is a replacement for MSMQ which was used in previous version of Lync. Therefore, it is part of the Front End servers and it is located under LYNCLOCAL named instance. It is also used for Archiving integration and Unified Contact Center. Currently, it supports Exchange and SQL for archiving.

Resolution

Set the EnableServerConversationHistory client policy to FALSE. Flush the database and restart the server using specific guidance from Microsoft.

Configure Exchange Partner configuration with Skype Server with OAUTH and test before turning on the EnableServerConversationHistory policy.