what's mean of "enqueue hash chains" latch?
- From: eygle <oracle.unix@xxxxxxxxx>
- To: oracle-l@xxxxxxxxxxxxx
- Date: Sat, 8 Jan 2005 21:55:55 +0800
hello;
We have a Oracle 8.1.7.0.0 Database on Solaris8.
With a parallel insert , database slow down heavy suddently.
I find lots of latch wait in database,from statspack(with 15 minutes
elapse) list:
Pct Avg Pct
Get Get Slps NoWait NoWait
Latch Name Requests Miss /Miss Requests Miss
----------------------------- -------------- ------ ------ ------------ ------
active checkpoint queue latch 260 0.0 0
cache buffers chains 47,228,551 0.0 552 0.0
checkpoint queue latch 3,263 0.0 0
dml lock allocation 46,899,746 12.1 0.0 0
enqueue hash chains 46,899,333 39.2 0.0 0
enqueues 849 0.0 0
job_queue_processes parameter 12 0.0 0
ktm global data 2 0.0 0
library cache 32,739 0.0 0.0 0
library cache load lock 70 0.0 0
list of block allocation 36 0.0 0
and
Latch Sleep breakdown for DB: QCB Instance: qcb Snaps: 150 -151
-> ordered by misses desc
Get Spin &
Latch Name Requests Misses Sleeps Sleeps 1->4
-------------------------- -------------- ----------- ----------- ------------
enqueue hash chains 46,899,333 18,367,985 6,312 18361675/630
8/2/0/0
dml lock allocation 46,899,746 5,678,834 1,228 5677606/1228
/0/0/0
-------------------------------------------------------------
Latch Miss Sources for DB: QCB Instance: qcb Snaps: 150 -151
-> only latches with sleeps are shown
-> ordered by name, sleeps desc
NoWait Waiter
Latch Name Where Misses Sleeps Sleeps
------------------------ -------------------------- ------- ---------- -------
dml lock allocation ktaiam 0 615 444
dml lock allocation ktaidm 0 604 784
enqueue hash chains ksqrcl 0 3,778 3,453
enqueue hash chains ksqgtl3 0 2,472 2,832
-------------------------------------------------------------
I can not find more info about "enqueue hash chains".
What' s it mean and how to reduce it ?
The SQL of parallel insert is :
insert /*+ append parallel(fc_costgatherresult_m,4) */ into
fc_costgatherresult_m
(kjnd,kjqj,pk_dwbm,pk_deptdoc,pk_psndoc,isproduct,pk_productorbalance,accountcurrtype,producttype,pk_costitem,originaldwbm,originaldept,calmny,pk_client,clienttype,pk_credittype)
select /*+ parallel(fc_costcalresult_m,4) */
'2004','11',pk_dwbm,pk_deptdoc,pk_psndoc,isproduct,pk_productorbalance,accountcurrtype,producttype,pk_costitem,originaldwbm,originaldept,sum(calmny),pk_client,clienttype,pk_credittype
from fc_costcalresult_m where pk_dwbm = originaldwbm
group by
pk_dwbm,pk_deptdoc,pk_psndoc,isproduct,pk_productorbalance,accountcurrtype,producttype,pk_costitem,originaldwbm,originaldept,pk_client,clienttype,pk_credittype
All the table is partition table.
Table fc_costcalresult_m with nearly 40G data.
And we have the parameter:
dml_locks = 2000
enqueue_resources = 2200
I also want to know why "dml lock allocation" Requests is so high?
Any suggestion is appreciate.
----------------------------------------
eygle from China.
my site: http://www.eygle.com
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