You typically create window groups only when you are in the role of Scheduler administrator.
You can group windows for ease of use in scheduling jobs. If a job must run during multiple time periods throughout the day, week, and so on, you can create a window for each time period, and then add the windows to a window group. You can then set the schedule_name attribute of the job to the name of this window group, and the job executes during all the time periods specified in the window group.
For example, if you had a window called "Weekends" and a window called "Weeknights," you could add these two windows to a window group called "Downtime." The data warehousing staff could then create a job to run queries according to this Downtime window group—on weeknights and weekends—when the queries could be assigned a high percentage of available resources.
If a window in a window group is already open, and a new job is created that points to that window group, the job is not started until the next window in the window group opens.
See "Creating Window Groups" for examples of creating window groups.