When lots of users log on Outlook Web App in an integration environment of Microsoft Exchange Server 2013 and Microsoft Lync Server, lots of log files are generated in the following folder:
C:\Program Files\Microsoft\Exchange Server\V15\Logging\OWA\InstantMessaging


This issue occurs because a LyncIMSyncLogEnabled key is enabled for Outlook Web App. This is by default. Therefore, you experience high usage of disk and system resource.


To resolve this issue, install the following update:

2936880 Cumulative Update 5 for Exchange Server 2013


To work around this issue, change the value of the LyncIMSyncLogEnabled key to false in the web.config file that is located in the following path:
Exchange install path\Exchange Server\v15\client access\owa\web.config 
For example, the existing code is as follows:

<add key="LyncIMSyncLogEnabled" value="true" /> 

Change to the following code:

<add key="LyncIMSyncLogEnabled" value="false" />


Microsoft has confirmed that this is a problem in the Microsoft products that are listed in the "Applies to" section.

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