1.Open PowerShell
2.Run the following commands:
a. Load client OM assembly.

     [Reflection.Assembly]::Load("Microsoft.TeamFoundation.Client, Version=, Culture=neutral, PublicKeyToken=b03f5f7f11d50a3a");
     $collectionBaseUrl = "http://YOURTFSSERVER:8080/tfs/YOURCOLLECTION/";
     $tfs = [Microsoft.TeamFoundation.Client.TeamFoundationServerFactory]::GetServer($collectionBaseUrl);
     $collectionHive = $tfs.GetService([Microsoft.TeamFoundation.Framework.Client.ITeamFoundationRegistry]);

b. Set the setting

     $collectionHive.SetValue("/Service/Integration/Settings/NotificationJobLogLevel", "2");

Note: Do not forget to change it back to 0 otherwise it might generates a lot of detailed errors to eat up your space…if you do have a lot of errors. I guess you will want to take care that too if it does happen 🙂