-- Routine tasks to be executed later
QueuedJob
    content             Value
    creationInstance    InstanceId         -- multiple uni2work instances access the same database, but each job must be only executed once
    creationTime        UTCTime
    lockInstance        InstanceId Maybe   -- instance that has started to execute this job
    lockTime            UTCTime Maybe      -- time when execution had begun
    deriving Eq Read Show Generic Typeable
CronLastExec
    job                 Value
    time                UTCTime
    instance            InstanceId
    UniqueCronLastExec job