LySS => Lync storage Service. It’s an SQL DB in all Front-end Servers.
We had MSMQ in Lync 2010 and the previous version. As a replacement for MSMQ, we have LySS. This DB is part of the FE instance LYNCLOCAL and mainly used for High Availability.
LySS mostly contains the data before committed to Monitoring(CDR &QOE) and Archiving(LcsLog) data. ie: whatever changes from server end stores in this DB and then transported to the monitoring and archiving DB’s.
LySS has a limitation that it could contain only 10 GB of Data.