This timeout is used by jobs trying to acquire an exclusive access to the warehouse resources during the Schema Change stage. ...

This timeout is used by jobs trying to acquire an exclusive access to the warehouse resources during the Schema Change stage.  SchemaUpdateWaitSeconds is how long a job will be waiting in the Running state for the exclusive access to call IWarehouseAdapter.SchemaChange(). If the timeout expires before the Schema Change is finished, the job quits and try at a later (scheduled) time.