关于scheduler相关的概念

Scheduler 中的Program对象并不是常规意义上的"程序"或"应用"，而就是一个"对象"，由
DBA定义的，具有执行某项功能的特殊对象。Program中实际执行的操作可以分为下列三种类
型：
1.PL/SQL BLOCK ：标准的pl/sql 代码块；
2.STORED PROCEDURE ：编译好的PL/SQL 存储过程，或者Java 存储过程，以及外部的c 子
程序；
3.EXECUTEABLE ：ORACLE 数据库之外的应用，比如操作系统命令等等。
实际上SCHEDULER 中创建job 时，也可以指定执行外部的程序。SCHEDULER 中的Job 更
像是之前版本继承过来的JOBS，只不过10g 中SCHEDULER 管理的JOBS 功能更加强大。
Programs 与Jobs 不同的是，Jobs 是定义好的，定时执行的任务，而Programs 则是定义好
的，等待被执行的对象。
• A window is represented by an interval of time with awell-defined beginning and
end,and is used to activate different resource plans at differenttimes. This allows
you to change resource allocation during a time period such as timeof day or time
of the sales year.
• A window group represents a list of windows, and allows foreasier management of
windows. You can use a window or window group as the schedule for ajob to ensure
that the job runs only when a window and its associated resourceplan are active.
• A job class defines a category of jobs that share common resourceusage requirements
and other characteristics. A job class groups jobs into largerentities.
• A resource consumer group associated with the job classdetermines the resources
that are allocated to the jobs in the job class.
• A resource plan enables users to prioritize resources (mostnotably CPU) among
resource consumer groups.