Richard Schwendiman explains the Centralized Logging Service (CLS) feature that was introduced in Lync Server 2013.
f you’ve had to troubleshoot server side issues in an OCS\Lync environment then you are familiar with OCSLogger.exe tool. The OCSLogger tool is installed as part of the debugging tools which can be download from the Microsoft Download Center (link below). Although this is a great tool for collecting data it has one major downside “Lack of Centralization”. So this means that when troubleshooting issues you would have to go to each OCS\Lync server, set your logging levels and flags, start logging, repro the issue, stop logging, and then analyze each log individually. This turned into a major project if you had a lot of servers that data was collected on. With the introduction of 2013, logging got a significant overhaul, now named CentralizedLogging Service (CLS).
Read more at source: http://blogs.technet.com/b/rischwen/archive/2014/02/10/lync-2013-centralized-logging-cls-customizing-scenarios.aspx