Oracle Study之--Oracle等待事件（7）
11:25:2name1 SYS@ prod>selectname from v$event_name where name like 'latch%' order by 1;NAME
----------------------------------------------------------------
latch activity
latch free
latch: Change Notification Hash table latch
latch: In memory undo latch
latch: MQL Tracking Latch
latch: PX hash array latch
latch: Undo Hint Latch
latch: WCR: processes HT
latch: WCR: sync
latch: cache buffer handles
latch: cache buffers chains
latch: cache buffers lru chain
latch: call allocation
latch: change notification client cache latch
latch: checkpoint queue latch
latch: enqueue hash chains
latch: gc element
NAME
----------------------------------------------------------------
latch: gcs resource hash
latch: ges resource hash list
latch: lob segment dispenser latch
latch: lob segment hash table latch
latch: lob segment query latch
latch: messages
latch: object queue header operation
latch: parallel query alloc buffer
latch: redo allocation
latch: redo copy
latch: redo writing
latch: row cache objects
latch: session allocation
latch: shared pool
latch: undo global data
latch: virtual circuit queues
33 rows selected.
11:39:21 SYS@ prod>select EVENT#,EVENT_ID,NAME,PARAMETER1,PARAMETER2,PARAMETER3from v$event_name
2* where name like '%latch free%'
EVENT# EVENT_ID NAME PARAMETER1 PARAMETER2 PARAMETER3
---------- ---------- ------------------------------ ---------- -------------------- ------------------------------
402 3474287957 latch free address number tries
409 2530878290 wait list latch free address number tries
11:32:33 SYS@ prod>desc v$latchname
Name Null? Type
----------------------------------------------------------------- -------- --------------------------------------------
LATCH# NUMBER
NAME VARCHAR2(64)
HASH NUMBER
所以latch free 等待事件在10g以后的版本中并不常见，而是以具体的Latch 等待事件出现。这个等待事件有三个参数：Address: 会话等待的latch 地址。Number： latch号，通过这个号，可以从v$latchname 视图中找到这个latch 的相关的信息，Tries: 会话尝试获取Latch 的次数。
11:34:25 SYS@ prod>select * from v$latchname
11:34:36 2where name like '%buffer%';
LATCH# NAME HASH
---------- ---------------------------------------------------------------- ----------
33 SGA IO buffer pool latch 2719726273
63 IPC stats buffer allocation latch 1449990452
106 KJC global post event buffer 3098969798
145 cache buffers lru chain 3559635447
146 buffer pool 510014793
150 cache buffers chains 3563305585
151 cache buffer handles 892398878
196 media recovery process out of buffers 2731251867
197 mapped buffers lru chain 93631960
208 lock DBA buffer during media recovery 3620457631
350 virtual circuit buffers 1577520421
378 parallel query alloc buffer 291345605
416 image handles of buffered messages latch 3223585260
476 buffer pin latch 3925519355
14 rows selected.
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