What are V$Session_Wait VS V$Session_event?
 
 Both of these tables are view In database , we will talk about what is the difference between them and Why some of record appear in V$Session_wait but not in V$session_event , Simple Topic But useful and good to know , Also Check the document that i post For Oracle that gave you structure for both of these view :

V$SESSION_WAIT
displays the current or last wait for each session.

V$SESSION_EVENT
lists information on waits for an event by a session

This is simulation for both table appear what is the common between two view :

    Conn test/test
    
    select SID, EVENT from v$session_wait where event='DIAG idle wait';
    
    SID          EVENT
    5   DIAG idle wait
    8   DIAG idle wait
    
    select SID,EVENT from v$session_event where event ='DIAG idle wait' ;
    
    SID          EVENT
    5   DIAG idle wait
    8   DIAG idle wait

Also its good to know when you are using 10g or later you can use v$seesion which is  gives you real-time information, what is happening right now.


gives you real-time information, what is happening right now :


there's different type of enqueue:wait in Oracle like the following :


    enq: TX - allocate ITL entry

    enq: TX - contention

    enq: TX - index contention

    enq: TX - row lock contention




to check them you can query V$EVENT_NAME view provides a

complete list of all the enq: wait events.


But in V$session_wait you can check the following :


     P1: Lock TYPE (or name) and MODE



    P2: Resource identifier ID1 for the lock



    P3: Resource identifier ID2 for the lock


 Which is not found in v$session_event .

So We can say :

V$SESSION_WAIT
displays the events for which sessions have just completed waiting or are currently waiting.
V$SESSION_EVENT
is similar to V$SYSTEM_EVENT, but displays all waits for each session.

 Reference Document :
1-V$session_wait
2-V$session_event
3-Events


Thanks.
NJ