The dynamic performance views are provided and managed by the database server. They can be accessed by the database administrator account SYS and are continuously updated when a database is used. You can use the dynamic performance views to monitor the performance of a database.
Overview
The Oracle mode of OceanBase Database provides a set of basic views that are managed by the database server and are accessible to the database administrator account SYS. The views are dynamic because they are continuously updated when a database is open and in use. The dynamic performance views provide information about the performance of a database.
The database administrator can query and create views on tables and grant other users the privileges to access the dynamic performance views.
The SYS account owns dynamic performance tables whose names are prefixed with V$. The SYS account can create views on the dynamic performance tables. Then, the SYS account can create public synonyms. The public synonyms that are created on the dynamic performance views share the prefix V$. For example, a dynamic performance view named V$DBLINK contains information about database links.
Types
The supported types of dynamic performance views are V$ 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.