How to Check Wait Event in Oracle Database

DBA scripts to Check Wait Event in Oracle Database:

SQL > set colsep '|'
   set pagesize 2000
   set linesize 150
   column username format a15
   column sid format 9999
   column status format a10
   column event format a30
   column name format a30
   column p1 format a20
   column p2 format a20
   column p3 format a20
 SQL > 			select v.sid,
   v.username username,
   v.status status,
   n.name,
   w.state,
   n.parameter1 || ' : ' || w.p1 p1,
   n.parameter2 || ' : ' || w.p2 p2,
   n.parameter3 || ' : ' || w.p3 p3
   from v$session v, v$event_name n , v$session_wait w
   where v.username is not null
   and w.event = n.name
   and w.sid=v.sid
   and w.event not in('null event')
   and v.STATUS='ACTIVE'
   /

Example:

SID|USERNAME       |STATUS    |NAME                          |STATE              |P1                  |P2                  |P3
-----|---------------|----------|------------------------------|-------------------|--------------------|--------------------|--------------------
 4914|PUBLIC         |ACTIVE    |class slave wait              |WAITING            |slave id : 0        | : 0                | : 0
 4536|PUBLIC         |ACTIVE    |class slave wait              |WAITING            |slave id : 0        | : 0                | : 0
 3027|PUBLIC         |ACTIVE    |class slave wait              |WAITING            |slave id : 0        | : 0                | : 0
 4540|P1RPHWGBM      |ACTIVE    |db file sequential read       |WAITING            |file# : 103         |block# : 1490384    |blocks : 1
 3023|P1RPHWGBM      |ACTIVE    |direct path read              |WAITED SHORT TIME  |file number : 105   |first dba : 1383936 |block cnt : 128
   23|P1RPHWGBM      |ACTIVE    |PX Deq: Table Q Normal        |WAITED KNOWN TIME  |sleeptime/senderid :|passes : 3          | : 0
     |               |          |                              |                   | 200                |                    |
  2289|P1RPHWGBM      |ACTIVE    |SQL*Net message to client     |WAITED SHORT TIME  |driver id : 14136975|#bytes : 1          | : 0
     |               |          |                              |                   |36                  |                    |
  1888|SYS            |ACTIVE    |SQL*Net message to client     |WAITED SHORT TIME  |driver id : 16508152|#bytes : 1          | : 0
     |               |          |                              |                   |32                  |                    |
  4178|P1RPHWGBM      |ACTIVE    |enq: PS - contention          |WAITING            |name|mode : 13476167|instance : 1        |slave ID : 4
     |               |          |                              |                   |74                  |                    |
  4927|P1RPHWGBM      |ACTIVE    |enq: BF - allocation contentio|WAITING            |name|mode : 11118837|node#/parallelizer# |bloom# : 0
     |               |          |                              |                   |82                  |: 875663873         |