RE: Insert into parent table gives row exclusive locks on the child tables in 11g
Date: Mon, 6 Jul 2009 18:06:49 -0700 (PDT)
Best guess based on your description would be some fix has caused this.
I think it would be because of the fix mentioned in
Bug 5909305 Change to DML lock modes for foreign key constraints
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- On Tue, 7/7/09, Reardon, Bruce (RTABBAY) <Bruce.Reardon_at_riotinto.com> wrote:
From: Reardon, Bruce (RTABBAY) <Bruce.Reardon_at_riotinto.com>
Subject: RE: Insert into parent table gives row exclusive locks on the child tables in 11g
Received: Tuesday, 7 July, 2009, 9:04 AM
I have now found
https://metalink.oracle.com/metalink/plsql/showdoc?db=NOT&id=223303.1 which describes that the Row-S locks on the child tables were introduced in 9.2.0 to address problems with parallel DML hanging.
I have logged a SR with Oracle, but would also appreciate any comments on why 11g shows Row-X locks on the child tables. Or if others see this in 126.96.36.199 / their 188.8.131.52.
Sent: Friday, 3 July 2009 4:40 PM
<< paraphrased >>
We have recently upgraded from 184.108.40.206 to 220.127.116.11 on Windows 2003R2 SP2 32 bit and have experienced a block lock situation involve foreign keys. We do not think it is due to missing indexes.
We don't yet have a full reproducer that does not rely on our full database, but do have a cut down example that shows the exclusive locks on the child tables. In this case, updates to the child tables are not blocked.
The question - why did 11g change the child locks to being row
This may help us understand why in the full example we get child updates blocked.
The reproducer can be found at
In 18.104.22.168, we see a TM DML enqueue lock Row-X (SX) on the parent_tbl.
In 9.2 and 10.2 we see the addition of "TM DML enqueue lock Row-S
(SS)" on the 2 child tables.
In 22.214.171.124, we see the lock on the child tables is now row exclusive - "TM DML enqueue lock Row-X (SX)".
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