檢視等待事件

--v$session_wait檢視中的p1、p2、p3表示等待事件的具體含義，如果wait event是db file scattered read,那麼p1=file_id/p2=block_id/p3=blocks,然後通過dba_extents即可

確定出熱點物件.

--如果是latch free的話,那麼p2為閂鎖號,它指向v$latch.

--求等待事件及其對應的latch

col event format a32;

col name format a32;

select sid,event,p1 as "p1 as file_id", p2 as "p2 as block_id/latch", p3 as "p3 as blocks",l.name

from v$session_wait sw,v$latch l

where event not like '%sql%' and event not like '%rdbms%' and event not like '%mon%' and sw.p2 = l.latch#(+);

--求等待事件及其熱點物件

col owner format a18;

col segment_name format a32;

col segment_type format a32;

select owner, segment_name, segment_type from dba_extents

where file_id = &file_id and &block_id between block_id and block_id + &blocks - 1;

--綜合以上兩條sql,同時顯示latch及熱點物件(速度較慢)

select sw.sid, event, l.name, de.segment_name from v$session_wait sw, v$latch l, dba_extents de

where event not like '%sql%' and event not like '%rdbms%' and event not like '%mon%'

and sw.p2 = l.latch#(+) and sw.p1 = de.file_id(+) and p2 between de.block_id and de.block_id + de.blocks - 1;

--如果是非空閒等待事件,通過等待會話的sid可以求出該會話在執行的sql

select sql_text from v$sqltext_with_newlines st, v$session se

where st.address = se.sql_address and st.hash_value = se.sql_hash_value and se.sid = &wait_sid order by piece;