how to resolve a hang in database

Starting from 11g, there is a welcome change though – there’s a new V$WAIT_CHAINS view, which lists all the hangs it has detected, it’s RAC-aware and is accessible via plain SQL. No need to run oradebug anymore, assuming that you are able to log on to query that V$ view :-)


From note 


Basic Information

SQL> SELECT chain_id, num_waiters, in_wait_secs, osid, blocker_osid, substr(wait_event_text,1,30)
 FROM v$wait_chains; 2

 ---------- ----------- ------------ ------------------------- ------------------------- ------------------------------
 1 0 10198 21045 21044 enq: TX - row lock contention
 1 1 10214 21044 SQL*Net message from client 

Additional Information (formatted) - Top 100 wait chain processes

 set pages 1000
 set lines 120
 set heading off
 column w_proc format a50 tru
 column instance format a20 tru
 column inst format a28 tru
 column wait_event format a50 tru
 column p1 format a16 tru
 column p2 format a16 tru
 column p3 format a15 tru
 column Seconds format a50 tru
 column sincelw format a50 tru
 column blocker_proc format a50 tru
 column waiters format a50 tru
 column chain_signature format a100 wra
 column blocker_chain format a100 wra

 FROM (SELECT 'Current Process: '||osid W_PROC, 'SID '||i.instance_name INSTANCE,
 'INST #: '||instance INST,'Blocking Process: '||decode(blocker_osid,null,'<none>',blocker_osid)||
 ' from Instance '||blocker_instance BLOCKER_PROC,'Number of waiters: '||num_waiters waiters,
 'Wait Event: ' ||wait_event_text wait_event, 'P1: '||p1 p1, 'P2: '||p2 p2, 'P3: '||p3 p3,
 'Seconds in Wait: '||in_wait_secs Seconds, 'Seconds Since Last Wait: '||time_since_last_wait_secs sincelw,
 'Wait Chain: '||chain_id ||': '||chain_signature chain_signature,'Blocking Wait Chain: '||decode(blocker_chain_id,null,
 '<none>',blocker_chain_id) blocker_chain
 FROM v$wait_chains wc,
 v$instance i
 WHERE wc.instance = i.instance_number (+)
 AND ( num_waiters > 0
 OR ( blocker_osid IS NOT NULL
 AND in_wait_secs > 10 ) )
 ORDER BY chain_id,
 num_waiters DESC)

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