About Maintenance Windows【每日一译】--2013-1-30

A maintenance window is a contiguous time interval during which automated maintenance tasks are run. Maintenance windows are Oracle Scheduler windows that belong to the window group named MAINTENANCE_WINDOW_GROUP. A Scheduler window can be a simple repeating interval (such as "between midnight and 6 a.m., every Saturday"), or a more complex interval (such as "between midnight and 6 a.m., on the last workday of every month, excluding company holidays").

When a maintenance window opens, Oracle Database creates an Oracle Scheduler job for each maintenance task that is scheduled to run in that window. Each job is assigned a job name that is generated at run time. All automated maintenance task job names begin with ORA$AT. For example, the job for the Automatic Segment Advisor might be called ORA$AT_SA_SPC_SY_26. When an automated maintenance task job finishes, it is deleted from the Oracle Scheduler job system. However, the job can still be found in the Scheduler job history.

一个维护窗口是一段相邻时间间隔，此间隔位于自动维护任务运行期间；维护窗口是O计划安排窗口，它属于窗口组名称叫作“MAINTEANCE_WINDOW_GROUP”。一个计划安排

窗口可以是一个简单重复间隔（比如“在凌晨和凌晨6点间，每个星期六），或一个更复杂的间隔（比如位于凌晨到凌晨6点，在每个月的最后一个工作日，不包含公司规定节假日”）。

当一个维护窗口打开时，O创建的计划安排任务为了每个计划窗口的维护任务。每个任务在任务运行的时间指定一个任务名。所以自动维护任务工作的命名都以ORA$AT开头。比如，自动段顾问可能是叫作“ORA$AT_SA_SPC_SY_26”。当一个自动段任务完成时，它将从O的计划安排任务系统中删除，不过此工作任务仍然可以计划工作历史中被发现。

In the case of a very long maintenance window, all automated maintenance tasks except Automatic SQL Tuning Advisor are restarted every four hours. This feature ensures that maintenance tasks are run regularly, regardless of window size.

对于一个非常长的维护窗口，所有自动维护任务除了自动SQL调试顾问都是在每4个钟重启的。这个功能确保了维护任务的运行规范，不需要理会窗口大小。

The framework of automated maintenance tasks relies on maintenance windows being defined in the database. Table 26–1 on page 26-7 lists the maintenance windows that are automatically defined with each new Oracle Database installation

自动维护任务的架构依赖于在数据库中定义的维护窗口。Table 26–1 on page 26-7列出了在每个数据库安装时自动定义的维护窗口。