[ovirt-users] mantenance mode error

hello, I must put in maintenance mode the node of ovirt but returns the following error (by admin web page): Error while executing action: Cannot switch Host to Maintenance mode. Host has asynchronous running tasks, wait for operation to complete and retry. I have checked the log file engine.log and returns the following errors: 2016-06-30 13:31:35,688 INFO [org.ovirt.engine.core.bll.MaintenanceNumberOfVdssCommand] (default task-47) [5f3d36f7] Lock Acquired to object 'EngineLock:{exclusiveLocks='null', sharedLocks='[00000001-0001-0001-0001-00000000037d=<POOL, ACTION_TYPE_FAILED_OBJECT_LOCKED>]'}' 2016-06-30 13:31:35,692 WARN [org.ovirt.engine.core.bll.MaintenanceNumberOfVdssCommand] (default task-47) [5f3d36f7] CanDoAction of action 'MaintenanceNumberOfVdss' failed for user admin@internal. Reasons: VAR__TYPE__HOST,VAR__ACTION__MAINTENANCE,VDS_CANNOT_MAINTENANCE_SPM_WITH_RUNNING_TASKS 2016-06-30 13:31:35,692 INFO [org.ovirt.engine.core.bll.MaintenanceNumberOfVdssCommand] (default task-47) [5f3d36f7] Lock freed to object 'EngineLock:{exclusiveLocks='null', sharedLocks='[00000001-0001-0001-0001-00000000037d=<POOL, ACTION_TYPE_FAILED_OBJECT_LOCKED>]'}' how can I do to see if there are tasks? What can i do for resolve the problem? Thanks in advance Nicola