C Oracle Wait Events

This appendix describes Oracle wait events.

It includes these topics:

Information about wait events is displayed in three dynamic performance views:

  • V$SESSION_WAIT displays the events for which sessions have just completed waiting or are currently waiting.

  • V$SYSTEM_EVENT displays the total number of times all the sessions have waited for the events in that view.

  • V$SESSION_EVENT is similar to V$SYSTEM_EVENT, but displays all waits for each session.

Many of these wait events are tied to the internal implementation of Oracle and therefore are subject to change or deletion without notice. Application developers should be aware of this and write their code to tolerate missing or extra wait events.

The following SQL statement displays an alphabetical list of all Oracle wait events and the wait class to which they belong:

SQL> SELECT name, wait_class FROM V$EVENT_NAME ORDER BY name;