[ovirt-users] Mantenance mode error

Hi, I have a problem. I try to put in maintenance mode the host, but the message that is displayed is this "Error while executing action: Cannot switch Host to Maintenance mode. Host has asynchronous running tasks, wait for operation to complete and retry." I checked the log file engine.log: "2016-10-10 14:32:53,841 INFO [org.ovirt.engine.core.bll.MaintenanceNumberOfVdssCommand] (default task-15) [697e9736] Lock Acquired to object 'EngineLock:{exclusiveLocks='null', sharedLocks='[00000001-0001-0001-0001-00000000016a=<POOL, ACTION_TYPE_FAILED_OBJECT_LOCKED>]'}' 2016-10-10 14:32:53,843 WARN [org.ovirt.engine.core.bll.MaintenanceNumberOfVdssCommand] (default task-15) [697e9736] Validation of action 'MaintenanceNumberOfVdss' failed for user admin@internal-authz. Reasons: VAR__TYPE__HOST,VAR__ACTION__MAINTENANCE,VDS_CANNOT_MAINTENANCE_SPM_WITH_RUNNING_TASKS 2016-10-10 14:32:53,843 INFO [org.ovirt.engine.core.bll.MaintenanceNumberOfVdssCommand] (default task-15) [697e9736] Lock freed to object 'EngineLock:{exclusiveLocks='null', sharedLocks='[00000001-0001-0001-0001-00000000016a=<POOL, ACTION_TYPE_FAILED_OBJECT_LOCKED>]'}' 2016-10-10 14:32:53,851 ERROR [org.ovirt.engine.api.restapi.resource.AbstractBackendResource] (default task-15) [] Operation Failed: [Cannot switch Host to Maintenance mode. Host has asynchronous running tasks," How can I revolve? Regards Nicola