Dynamic performance views are maintained by the database server and are accessible to the database administrator user SYS. These views are continuously updated when the database is opened and in use, and their content primarily relates to performance.
Overview
The Oracle mode of OceanBase Database provides a set of base views maintained by the database server in the schema. These views are accessible to the database administrator user SYS. Because they are continuously updated when the database is opened and in use, and their content primarily relates to performance, these views are known as dynamic performance views.
The database administrator can query and create views on tables and grant access to these views to other users.
The SYS user has access to dynamic performance tables, which have names starting with V$. Views can be created on these tables, and they can be accessed using public synonyms with the prefix V$. For example, the V$DBLINK view contains information about database Links.
Types
The supported types of dynamic performance views are V$ and GV$ views.
V$ views
Dynamic performance views are identified by the prefix V$. The public synonyms that are created on these views share the prefix V$. Database administrators and other users must access only the objects to which the public synonyms with the prefix V$ point.
After a database instance is started, you can access the V$ views that are read from the memory.
GV$ views
In most cases, a V$ view corresponds to a GV$ view, which is a global V$ view. If you query a GV$ view in an OceanBase cluster, the V$ view information from all qualified database instances is returned.
Storage of dynamic performance views
Dynamic performance views are created based on virtual tables that are created from database memory structures. Dynamic performance views are also called fixed views. A database administrator cannot modify or remove dynamic performance views.
They are not conventional tables that are stored in a database. Read consistency is not guaranteed for the dynamic performance views because data is updated in real time. Compared with regular database tables, dynamic performance views provide only data about internal disk structures and memory structures. You can query these views but you cannot update or modify them.
The dynamic performance views are not true tables. Therefore, data in these views varies based on the state of the cluster and service node.