---
---
User runs a program to load data into the DB. At a certain point, this
causes
an ORA-00060 (See ORA-00060.ora-code.com) (deadlock). So far no real problem, but a few minutes later
(while
deadlock cleanup is still going on), every other session in the DB hangs
until
deadlock cleanup is completed. 10046 traces of the hanging processes show
that
they are all waiting on 'latch free '; trace files contain almost nothing
but
lines of the type :
...
WAIT #6: nam= 'latch free ' ela= 207 p1=635234948 p2=13 p3=136
WAIT #6: nam= 'latch free ' ela= 206 p1=635234948 p2=13 p3=137
WAIT #6: nam= 'latch free ' ela= 206 p1=635234948 p2=13 p3=138
WAIT #6: nam= 'latch free ' ela= 207 p1=635234948 p2=13 p3=139
WAIT #6: nam= 'latch free ' ela= 206 p1=635234948 p2=13 p3=140
...
The latch with number p2=13 is the 'enqueue hash chains ' latch.
---
---
And Oracle 's answer :
---
---
The problem you see is when the ora-60 (See ora-60.ora-code.com) error will generate an systemstate
dump automatically.
Then we need to take enqueue locks of the structure and this is causing
your problems.
This behaviour can be changed by setting event 10027 in your init.ora
file,
Put this is your init.ora file.
---
---
mvg/regards
Jo
"Jonathan Lewis " <jonathan@(protected) >
Sent by: oracle-l-bounce@(protected)
01/09/2005 23:40
Please respond to jonathan
To: <oracle-l@(protected) >
cc:
Subject: Re: what 's mean of "enqueue hash chains " latch?
Note also how:
enqueue gets and releases = 23M
db block gets = 23 M
execute count = 23M
You can 't help feeling that that 's not a
complete coincidence. I think your trigger
theory sounds quite good at the moment,
only
a) I 'd like to find that 23M executions in
v$sql. Why isn 't it appearing in statspack ?
b) There 's no redo generated to match the
volume of locking.
I 'd like to see the snapshot of x$ksqst
One thought - for parallel DML, maybe
there are lots of DX locks being taken
and dropped.
Regards
Jonathan Lewis
http://www.jlcomp.demon.co.uk/faq/ind_faq.html
The Co-operative Oracle Users ' FAQ
http://www.jlcomp.demon.co.uk/seminar.html
Public Appearances - schedule updated Dec 23rd 2004
-- -- Original Message -- --
From: "Riyaj Shamsudeen " <rshamsud@(protected) >
To: <oracle.unix@(protected) >; <jonathan@(protected) >
Cc: <oracle-l@(protected) >
Sent: Sunday, January 09, 2005 9:09 PM
Subject: RE: what 's mean of "enqueue hash chains " latch?
Eygle
Looking at the excel spreadsheet, one of the child latch has 2.4
Billion gets and other child latches have less then 76K latch gets. So,
sessions are contending to lock one table. Looking at the statspack
report, you have numerous enqueue gets and releases too.
Is there any foreign key constraint on this table ? If yes, do
you have any index on that foreign key column ? Further, what mode locks
are being acquired ?
do you have any triggers on this table, by any chance ?
