In Adobe CQ5, it sometimes becomes necessary to make a particular package or class spit out DEBUG level log entries in order to troubleshoot problems.
1) From the error.log, determine the class that you want to bump up logging on. I.e. let’s say you’ve got system logging turned up to Warn and you want to see the INFO level progress of your datastore Garbage Collection (com.day.crx.persistence.tar.utils.DataStoreGarbageCollector)
2) Add a INFO logger configuration for that class.
In the OSGI configuration console at /system/console/configMgr , search for “Apache Sling Logger Configuration” and click the plus sign to its right. The class name should be in the field labelled “Logger”. See example below.