Oracle数据字典：$v_
除了上述视图之外，Oracle 还有一组用于记录当前数据库活动的虚拟表。顾名思义，动态性能表不是真实的表。因此，并不是所有用户都
除了上述视图之外，Oracle 还有一组用于记录当前数据库活动的虚拟表。顾名思义，动态性能表不是真实的表。因此，并不是所有用户都能访问这些表。但是，允许数据库管理员查询并创建这些表的视图，管理员还可授予其他用户访问这些视图的权限。
SYS 用户拥有动态性能表和所有以 V_$ 开头的表名。视图为这些表而创建，而同义词是为视图创建的。同义词名称以“V$”开头。
显示 V$SESSION 视图的状态、登录时间和用户名：
显示有关每个日志组的信息：
显示 V$DATABSE 视图中的数据库 ID、数据库名和日志模式：
可使用以下代码查询有关字典表的信息：
更多Oracle相关信息见Oracle 专题页面 ?tid=12
数据字典主要提供数据库中的所有信息，因此，此字典可用于通过各种视图来查看所需的数据。数据字典的只读格式可阻止任何用户对其进行编辑或修改。
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