Skype for Business Server 2015 databases are as same as it was in Lync Server 2013. Skype for Business Server 2015 installs SQL Server 2014 Express Edition (64-bit) for local configuration databases while SQL Server 2014/SQL Server 2012 SP2 with CU2/SQL Server 2008 R2 SP2 can be deployed for Back End databases, Archiving, Monitoring, Persistent Chat and Persistent Chat Compliance databases. Below are the graphical representation of databases placement in Standard and Enterprise Edition.
Explanation of each databases:
xds: xds is the main database of SfB Server and part of central management store which maintain the topology information, polices, configuration etc. and replicate a read only copy to each SfB server.
rtcxds: rtcxds maintains the backup for user data
rtcshared: rtcshared hosts the conferencing directory
rtcab: rtcab stands for real time communication address book and maintain the address book service information
cpsdyn: cpsdyn maintains the dynamic information database for Call Park application.
rgsconfig: rgsconfig maintains the response group configuration service data file.
rgsdyn: rgsconfig maintains the runtime data for response group configuration service data file.
xds: xds on SfB frontend server maintain a read only copy of xds database which is part of central management store and resides in SQL backend database server.
rtc: rtc store persistent users data such as contact list, schedule conferences and ACL’s etc.
rtcdyn: rtcdyn maintains dynamic user data such as presence.
lyss: lyss stands for Lync Storage Service and used to maintain HA within a FE pool. It is a blob database and abstract writes to backend 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.
lcslog: lcslog maintains data file for the retention of instant messaging and conferencing data on an Archiving Server.
cdr: cdr stands for call detail recording and maintains the call detail recording data.
QoE: QoE stands for quality of Experience and maintains the QoE data to provide best experience to SfB users.
mgc: maintains user persistent chat data.
mgccomp: maintains compliance data persistent chat.