"JBAS014122: Error during retrying timeout for timer - could not obtain lock within 5000MILLISECONDS" in EAP6

Issue

• Sometimes there is a JBAS014122 error for a @Singleton with a @Scheduled timer annotation, what is the reason?

ERROR [org.jboss.as.ejb3] (EJB default - 3) JBAS014122: Error during retrying timeout for timer: [id=06dd3820-e65b-4886-9a31-eceb54ae0542 timedObjectId=ejb31-timer.ejb31-timer.SimpleScheduleSingletonTimerBean auto-timer?:true persistent?:true timerService=org.jboss.as.ejb3.timerservice.TimerServiceImpl@5cd5fcdc initialExpiration=Fri Jun 26 00:00:00 CEST 2015 intervalDuration(in milli sec)=0 nextExpiration=Fri Jun 26 10:11:15 CEST 2015 timerState=RETRY_TIMEOUT: javax.ejb.ConcurrentAccessTimeoutException: JBAS014373: EJB 3.1 PFD2 4.8.5.5.1 concurrent access timeout on org.jboss.invocation.InterceptorContext$Invocation@1fd9f127 - could not obtain lock within 5000MILLISECONDS

• Why there is the following WARN message for a @Scheduled timer?

WARN  [org.jboss.as.ejb3] (EJB default - 2) JBAS014143: A previous execution of timer [ejb31-timer.ejb31-timer.SimpleScheduleSingletonTimerBean 7ca5dc65-9f66-4c5a-89f2-daa897388b1f] is still in progress, skipping this overlapping scheduled execution at: Fri Jun 26 10:07:00 CEST 2015 as timer state is IN_TIMEOUT