Oracle contains a set of underlying views that are maintained by the database server and accessible to the database administrator user SYS. These views are called dynamic performance views because they are continuously updated while a database is open and in use, and their contents relate primarily to performance.
Although these views appear to be regular database tables, they are not. These views provide data on internal disk structures and memory structures. You can select from these views, but you can never update or alter them.
The catalog.sql script contains definitions of the views and public synonyms for the dynamic
performance views. You must run catalog.sql to create these views and synonyms. After
installation, only user SYS or anyone with SYSDBA privilege has access to the dynamic
performance tables. See Oracle Database Administrator’s Guide for more information about
running catalog.sql.
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