Dynamic performance views (V$) are owned by SYS. The dynamic performance views maintained by the Oracle database instance reflect various database metrics since the time when the instance was started. There are three categories of V$ views: current state views, accumulated views, and information views.
The following is a list of a few important V$ views with a short description of each:
V$LOCK:
lists details of currently held locks in the databaseV$PROCESS:
displays information about currently active processesV$SESSION_EVENT:
provides information about the event that each session is waiting forV$SESSION_WAIT:
displays information about wait events for which active sessions are currently waitingV$SESSTAT:
displays statistics for all the sessions connected to the databaseV$SQLTEXT:
displays...