Symptoms
When you deploy Shared Line Appearance (SLA) in a Microsoft Skype for Business Server 2015 environment, the RtcHost.exe process consumes too much memory on a Skype for Business Server 2015 Front End server.
Resolution
To fix this issue, install the March 2018 cumulative update 6.0.9319.516 for Skype for Business Server 2015, Front End Server and Edge Server.