Oracle中的父閂大致可以分成2類：有子閂的父閂或者獨居的父閂，我們來看看這些父閂的屬性: SQL> select * from v$version; BANNER ---------------------------------------------------------------- Oracle Database 10g Enterprise Edition Release 10.2.0.4.0 - 64bi PL/SQL Release 10.2.0.4.0 - Production CORE 10.2.0.4.0 Production TNS for IBM/AIX RISC System/6000: Version 10.2.0.4.0 - Productio NLSRTL Version 10.2.0.4.0 - ProductionSQL> select count(distinct name) from v$latch_children; COUNT(DISTINCTNAME) -------------------82/* 10.2.0.4下共有82種不同子閂，同比11.2.0.1是75種，要比10g中少一些，因為一部分閂在11g中被mutex替代了 */ SQL> select count(distinct name) from v$latch_parent; COUNT(DISTINCTNAME) -------------------394/* 共有394種不同父閂 */SQL> select lp.name2 from v$latch_parent lp,(select distinct name from v$latch_children) lc3 where lp.name=lc.name(+) and lc.name is NULL;NAME -------------------------------------------------- temp lob duration state obj allocation alert memory latch mapped buffers lru chain resmgr:schema config QMT FAL subheap alocation SGA kcrrssncpl latch KJC global post event buffer Reserved Space Latch Request id generation latch kpon sga structure resmgr:runnable lists hash table modification latch xscalc freelist gcs pcm hashed value bucket hash parameter list KMG MMAN ready and startup request latch server alert latch bq:time manger info latch kwqbsn:qsga job queue sob latch KFCL Instance Latch qm_init_sga state object free list KFCL BX Freelist process logical standby view resmgr:queued list multiblock read objects hint flashback FBA barrier i/o slave adaptor ksxp tid allocation KJC receiver ctx free list In memory undo latch OS process: request allocation krbmrosl resmgr:running actses count active service list parallel recoverable recovery xssinfo freelist cache table scan latch XDB unused session pool queue sender's info. latch flashback hint SCN barrier RSM process latch first spare latch qmn task queue latch JS broadcast autostart latch constraint object allocation AW SGA latch KSFQ cached attr list loader state object freelist JS queue state obj latch shared server info dummy allocation peplm policy information Testing shrink stat allocation latch FOB s.o list latch media recovery process out of buffers KJC receiver queue access list flashback mapping shared server configuration ASM map operation freelist statistics aggregation resmgr:free threads list block media rcv so alloc latch ges statistic table query server freelists mostly latch-free SCN RSM SQL latch name-service entry name-service request threshold alerts latch name-service request queue ges process table freelist virtual circuits kupp process latch archive process latch Token Manager error message lists Memory Queue Message Subscriber #1 direct msg latch Memory Queue ges deadlock list gcs remastering latch logical standby cache resmgr group change latch KFK SGA context latch pass worker exception to master process group creation NSV creation/termination latch ksfv subheap Media rcv so alloc latch job_queue_processes parameter latch segmented array pool ASM map operation hash table name-service pending queue message enqueue sync latch KJC snd proxy ctx free list image handles of buffered messages latch KJCT receiver queue access XDB used session pool ASM file locked extent latch change tracking consistent SCN trace latch flashback sync request Policy Refresh Latch KFC SGA latch AQ Propagation Scheduling System Load DMON Work Queues Latch Streams Generic session state list latch OS process allocation gcs opaque info freelist shared server spare latch 2 KJC snd proxy queue access list KFC Hash Latch Bloom filter list latch resumable state object JS event notify broadcast latch Change Notification Hash table latch global ctx hash table latch alert log latch AQ Propagation Scheduling Proc Table reservation so alloc latch ksir sga latch KFM allocation ASM allocation dispatcher info Transportable DB Context Latch kwqbcco:cco SGA mapping latch kwqi:kchunk latch datapump attach fixed tables latch process allocation KJC destination ctx free list JS broadcast drop buf latch SQL memory manager latch resmgr:gang list compile environment latch slave class create JOX SGA heap latch MQL Tracking Latch shared server spare latch 1 ASM file allocation latch instance enqueue redo writing name-service memory objects bufq statistics session allocation global hanganlyze operation session timer gcs domain validate latch qmn state object latch NSV command ID generation latch ping redo on-disk SCN SGA kcrrlatmscnl latch JS broadcast load blnc latch KFMD SGA internal temp table object number allocation latc bug fix control action latch job_queue_processes free list latch Memory Queue Message Subscriber #4 kwqbsgn:msghdr enqueues cost function flashback marker cache AWR Alerted Metric Element list KFR redo allocation latch FIB s.o chain latch Memory Queue Message Subscriber #3 spilled messages latch gcs remaster request queue sequence cache managed standby latch KTF sga latch resmgr:vc list latch kmcpvec latch Memory Management Latch KJC global resend message queue name-service namespace objects shared server spare latch 3 resmgr:active threads ASM network background latch global KZLD latch for mem in SGA presentation list multiple dbwriter suspend ASM map headers query server process KFCL LE Freelist Managed Standby Recovery State lgwr LWN SCN rm cas latch file number translation table X$KSFQP archive control WCR: kecu cas mem JS broadcast add buf latch pebof_rrv KWQMN job cache list latch file cache latch resmgr:incr/decr stats Consistent RBA ges timeout list user lock kwqbsn:qxl kokc descriptor allocation latch hash table column usage latch dml lock allocation redo on-disk SCN LGWR NS Write Bloom Filter SGA latch KFA SGA latch ASM map load waiting list recovery domain freelist virtual circuit buffers object stats modification TXN SGA hot latch diags PL/SQL warning settings KPON ksr channel latch dynamic channels ges caches resource lists cache protection latch end-point list second spare latch ges s-lock bitvec freelist Mutex kmcptab latch rules engine rule statistics ASM rollback operations rules engine rule set statistics library cache load lock event group latch list of block allocation gcs drop object freelist STREAMS LCR KWQMN to-be-Stopped Buffer list Latch address list instance information ktm global data XDB Config SGA IO buffer pool latch active checkpoint queue latch JS broadcast kill buf latch DMON Process Context Latch Undo Hint Latch rules engine evaluation context statistics dictionary lookup event range base latch begin backup scn array fixed table rows for x$hs_session flashback FBA barrier ASM db client latch KSXR large replies buffer pin latch ges synchronous data FAL request queue gcs resource validate list SGA kcrrpinfo latch reg$ timeout service time transaction branch allocation Change Notification Latch Mutex Stats SGA kcrrgap latch KFC FX Hash Latch flashback allocation sort extent pool logminer work area KFC LRU latch OS file lock latch ksupkttest latch database property service latch NLS data objects Policy Hash Table Latch Memory Queue Message Subscriber #2 cache buffer handles queued dump request JS mem alloc latch device information ncodef allocation latch change tracking state change latch flashback SCN barrier temporary table state object allocation parallel txn reco latch ksuosstats global area rules engine aggregate statistics change tracking optimization SCN channel anchor parameter table allocation management OLS label cache vecio buf des STREAMS Pool Advisor cas latch Real time apply boundary Memory Queue Subscriber generalized trace enabling latch Fast-Start Failover State Latch DMON Network Error List Latch numer of job queues for server notfn messages ksv instance resmgr:method mem alloc latch QOL Name Generation Latch enqueue sob latch KMG resize request state object freelist Memory Management Parameter Latch KWQP Prop Status datapump job fixed tables latch312 rows selected./* 10.2.0.4中共有312個獨居的父閂 */SQL> select lp.name,lp.gets,lp.immediate_gets2 from v$latch_parent lp, (select distinct name from v$latch_children) lc3 where lp.name = lc.name(+)4 and lc.name is NULL5 and (lp.gets != 0 or lp.immediate_gets != 0) order by gets asc;NAME GETS IMMEDIATE_GETS -------------------------------------------------- ---------- -------------- RSM SQL latch 0 1 Undo Hint Latch 0 122 Memory Management Latch 0 4189799 MQL Tracking Latch 0 250886 recovery domain freelist 1 0 instance enqueue 1 0 QMT 1 0 gcs drop object freelist 1 0 channel anchor 1 0 reg$ timeout service time 1 0 address list 1 0 generalized trace enabling latch 1 0 global hanganlyze operation 1 0 rules engine evaluation context statistics 1 2 qm_init_sga 1 0 rules engine rule statistics 2 0 resmgr:vc list latch 2 0 ksv instance 2 0 Mutex Stats 2 0 managed standby latch 2 0 global ctx hash table latch 2 0 shared server configuration 3 2 resmgr:method mem alloc latch 3 0 alert log latch 5 2 qmn state object latch 6 0 NLS data objects 7 0 rules engine aggregate statistics 8 0 KJC receiver ctx free list 9 2 KJCT receiver queue access 9 0 KJC snd proxy ctx free list 9 0 KJC snd proxy queue access list 9 0 KJC receiver queue access list 9 0 name-service entry 11 0 job_queue_processes free list latch 13 2 KJC destination ctx free list 18 2 name-service namespace objects 22 2 cache table scan latch 24 12187349 event range base latch 94 0 JS broadcast kill buf latch 103 0 file number translation table 135 0 trace latch 526 0 temp lob duration state obj allocation 1831 0 ges synchronous data 3369 244198 KWQP Prop Status 3491 0 KSXR large replies 3796 0 JOX SGA heap latch 4006 1147 query server process 4458 4452 resmgr:schema config 6987 0 SQL memory manager latch 6998 4183835 state object free list 7012 0 temporary table state object allocation 7346 0 X$KSFQP 12112 0 internal temp table object number allocation latc 24327 0 name-service request 26760 0 slave class create 29562 0 JS mem alloc latch 42492 2 KTF sga latch 52471 2860365 FIB s.o chain latch 189472 0 ncodef allocation latch 207281 0 global KZLD latch for mem in SGA 213870 0 event group latch 250324 0 FAL subheap alocation 270455 0 FAL request queue 270455 0 dictionary lookup 293787 0 ktm global data 294500 0 rules engine rule set statistics 349119 0 hash table modification latch 410073 2 kwqbsn:qsga 447245 0 library cache load lock 451132 0 ges process table freelist 500374 0 OS process: request allocation 500376 0 process group creation 500376 0 object stats modification 504747 5 krbmrosl 654559 0 archive control 671384 0 gcs remaster request queue 720951 0 ksuosstats global area 851936 0 sort extent pool 931800 0 KWQMN job cache list latch 984125 0 loader state object freelist 1181736 0 error message lists 1276908 0 threshold alerts latch 1314860 0 hash table column usage latch 1665060 358586939 qmn task queue latch 1747101 0 statistics aggregation 1955529 0 parameter list 2321759 0 query server freelists 2425792 0 JS broadcast load blnc latch 2505489 0 job_queue_processes parameter latch 2681109 0 JS broadcast drop buf latch 2882525 0 JS broadcast add buf latch 2882597 0 ges timeout list 3193262 3404126 KMG MMAN ready and startup request latch 4189807 0 FOB s.o list latch 4211788 0 session timer 4341863 0 archive process latch 4745101 0 OS process allocation 4781454 0 begin backup scn array 5372508 0 parallel txn reco latch 7060020 0 ges deadlock list 8225144 3734 kokc descriptor allocation latch 10218320 0 ASM db client latch 10368227 0 compile environment latch 10408232 0 SGA IO buffer pool latch 10518957 10524060 parameter table allocation management 10580949 0 resmgr group change latch 10928225 0 file cache latch 12909240 0 cache buffer handles 20398694 0 user lock 20713291 0 gcs opaque info freelist 20714278 0 resmgr:free threads list 20855255 0 resmgr:active threads 20862246 0 dummy allocation 20870065 0 session state list latch 21249620 0 name-service pending queue 22618030 0 name-service memory objects 23624996 2 list of block allocation 23630931 0 active checkpoint queue latch 27637189 5 multiblock read objects 32939240 2 sequence cache 33287559 0 Consistent RBA 35761759 0 lgwr LWN SCN 36790265 0 mostly latch-free SCN 36976437 0 PL/SQL warning settings 41507388 0 active service list 58157997 4341784 queued dump request 62853955 0 JS queue state obj latch 90975988 0 ges caches resource lists 97073996 145681370 gcs remastering latch 107632668 0 process allocation 112440225 249864 AWR Alerted Metric Element list 129684638 0 redo writing 142555594 0 name-service request queue 148086376 0 dml lock allocation 156109225 0 transaction branch allocation 449472105 0 messages 670565488 0 session allocation 1648369839 0 enqueues 2505157425 0138 rows selected./* 以上列出了312個獨居父閂中有138個常被使用，其中最常用的是"enqueues"，"session allocation"，"messages"等父閂，若他們被某個dead process長期持有則可能導致整個實例hang住 *//* 注意一般RAC環境中才會用到ges caches resource lists等全局隊列閂 */SQL> select lp.name, lp.gets, lp.immediate_gets, lc.name2 from v$latch_parent lp, (select distinct name from v$latch_children) lc3 where lp.name = lc.name(+)4 and lc.name is not NULL5 and (lp.gets != 0 or lp.immediate_gets != 0)6 order by gets asc;NAME GETS IMMEDIATE_GETS NAME -------------------------------------------------- ---------- -------------- -------------------------------------------------- resmgr:resource group CPU method 1 0 resmgr:resource group CPU method simulator lru latch 2 0 simulator lru latch resmgr:plan CPU method 2 0 resmgr:plan CPU method recovery domain hash list 4 0 recovery domain hash list process queue 23 0 process queue process queue reference 48 0 process queue reference shared pool 57 0 shared pool enqueue hash chains 3613 0 enqueue hash chains library cache 27905 0 library cache redo allocation 28695 0 redo allocation JS slv state obj latch 155438 0 JS slv state obj latch undo global data 945519 0 undo global data transaction allocation 3327272 0 transaction allocation13 rows selected./* 82個有子閂的父閂中只有13個是常使用的，其中最常用的是"transaction allocation"，"undo global data","JS slv state obj latch" */ 有用的父閂被持有往往會釀成災難，因為他們在數據庫堪稱是真正one and only的。

轉載于:https://www.cnblogs.com/macleanoracle/archive/2010/09/07/2967528.html

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