637.Which three statements are true about windows? (Choose three.)
A. Only one window can be open at any given time
B. Consumer groups are associated with windows
C. Windows work with job classes to control resource allocation
D. The database service name must be provided during windows creation
E. Windows can automatically start job or change resource allocation among jobs for various time periods.
Answer: ACE
答案解析：
参考：http://docs.oracle.com/cd/E11882_01/server.112/e25494/schedover.htm#ADMIN13083
Because only one window can be active at one time--A正确。
Windows work with job classes to control resource allocation. ----C正确。
You create windows to automatically start jobs or to change resource allocation among jobs during various time periods of the day, week, and so on. --E正确。
Windows
You typically create windows only when you are in the role of Scheduler administrator.
You create windows to automatically start jobs or to change resource allocation among jobs during various time periods of the day, week, and so on. A window is represented by an interval of time with a well-defined beginning and end, such as "from 12am-6am".
Windows work with job classes to control resource allocation. Each window specifies the resource plan to activate when the window opens (becomes active), and each job class specifies a resource consumer group or specifies a database service, which can map to a consumer group. A job that runs within a window, therefore, has resources allocated to it according to the consumer group of its job class and the resource plan of the window.
Figure 28-2 shows a workday that includes two windows. In this configuration,
jobs belonging to the job class that links to Consumer Group 1 get more resources in the morning than in the afternoon. The opposite is true for jobs in the job class that links to Consumer Group 2.
Figure 28-2 Windows help define the resources that are allocated to jobs
Description of "Figure 28-2 Windows help define the resources that are allocated to jobs"
See Chapter 27, "Managing Resources with Oracle Database Resource Manager" for more information on resource plans and consumer groups.
You can assign a priority to each window. If windows overlap, the window with the highest priority is chosen over other windows with lower priorities. The Scheduler automatically opens and closes windows as window start times and end times come and go.
A job can name a window in its schedule_name attribute. The Scheduler then starts the job when the window opens. If a window is already open, and a new job is created that points to that window, the new job does not
start until the next time the window opens.
Overlapping Windows
Although Oracle does not recommend it, windows can overlap.
Because only one window can be active at one time, the following rules are used to determine which window is active when windows overlap:
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If windows of the same priority overlap, the window that is active will stay open. However, if the overlap is with a window of higher priority, the lower priority window will close and the window with the higher priority will open. Jobs currently running that had a schedule naming the low priority window may be stopped depending on the behavior you assigned when you created the job.
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If, at the end of a window, there are multiple windows defined, the window with the highest priority opens. If all windows have the same priority, the window that has the highest percentage of time remaining opens.
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An open window that is dropped automatically closes. At that point, the previous rule applies.
Whenever two windows overlap, an entry is written in the Scheduler log.