deadlock with replication's update/insert/delete process

We are using SQL 2K with sp4. We are using Push method and both publisher
and distribution db are on the same server.
Recently we have quite a few deadlocks involving a replication's sp such as
sp_MSupd_xxxxxxx and some select statement from our application. We have
deadlocks from time to time but I haven't seen a deadlock caused by sp_MSupd
until now. Is this an indication of something that I need to look into?
Any help is very much appreciated.
Wingman
Sounds like a transaction on the publisher is coming over as a transaction
on the subscriber which you're deadlocking with. Some ideas: you could look
at the order of the transaction on the publisher and check that your
application accesses tables in the same order. You could allow your
application to do dirty reads (not generally recommended but sometimes
useful). You could use SQL Server 2005 and the snapshot isolation level
where this problem goes away. Finally you could control when the
distribution agent runs to avoid the lcash.
Cheers,
Paul Ibison SQL Server MVP, www.replicationanswers.com .

Deadlock between Distribution Agent and Distribution Agent Cleanup

I am experiencing this problem. Deadlock of these two M$ stored
procedures :
sp_MSget_repl_commands (Executed by the Distribution Agent --pull
subscriber ) and
sp_MSdistribution_cleanup (Executed by the Distribution Agent Cleanup
job)
the offending queries are :

>From sp_MSdistribution_cleanup:
DELETE MSrepl_commands WITH (PAGLOCK) where
publisher_database_id = @.publisher_database_id and
xact_seqno <= @.max_xact_seqno

>From sp_MSget_repl_commands:
select @.max_xact_seqno = max(xact_seqno) from MSrepl_commands
(READPAST)
where
publisher_database_id = @.publisher_database_id and
command_id = 1 and
type <> -2147483611
I searched this and other groups and no convincing answer was posted.
Is there anyone experiencing this problem ? if so what did you do to
"resolve" it (not to decrease its frequency)
Thanks in Advance.
-Noel
Sr. DBA
I've seen this a lot, since they are both hitting the same repl table at the
same time, but I've never seen it fail/deadlock for extended periods of
time. If your agent failing, then succeeding?
Kevin Hill
3NF Consulting
http://www.3nf-inc.com/NewsGroups.htm
Real-world stuff I run across with SQL Server:
http://kevin3nf.blogspot.com
<zerg2k@.yahoo.com> wrote in message
news:1166732530.463614.305580@.i12g2000cwa.googlegr oups.com...
>I am experiencing this problem. Deadlock of these two M$ stored
> procedures :
> sp_MSget_repl_commands (Executed by the Distribution Agent --pull
> subscriber ) and
> sp_MSdistribution_cleanup (Executed by the Distribution Agent Cleanup
> job)
> the offending queries are :
>
> DELETE MSrepl_commands WITH (PAGLOCK) where
> publisher_database_id = @.publisher_database_id and
> xact_seqno <= @.max_xact_seqno
> select @.max_xact_seqno = max(xact_seqno) from MSrepl_commands
> (READPAST)
> where
> publisher_database_id = @.publisher_database_id and
> command_id = 1 and
> type <> -2147483611
> I searched this and other groups and no convincing answer was posted.
> Is there anyone experiencing this problem ? if so what did you do to
> "resolve" it (not to decrease its frequency)
> Thanks in Advance.
> -Noel
> Sr. DBA
>
|||Kevin,
This is not 'extreme' for me but the fact that those deadlocks are
happening makes me nervous in case the activity expands for more
extended periods. This is something that I would like to avoid if at
all possible.
and you are correct it fails, then retrys and if the 'high' activity
period some how subsides a bit it succeeds. I thought those lock hints
were pretty safe to avoid such situations but apparently I was wrong.
Thanks for the feedback.
-Noel
Sr DBA
Kevin3NF wrote:[vbcol=seagreen]
> I've seen this a lot, since they are both hitting the same repl table at the
> same time, but I've never seen it fail/deadlock for extended periods of
> time. If your agent failing, then succeeding?
> --
> Kevin Hill
> 3NF Consulting
> http://www.3nf-inc.com/NewsGroups.htm
> Real-world stuff I run across with SQL Server:
> http://kevin3nf.blogspot.com
>
> <zerg2k@.yahoo.com> wrote in message
> news:1166732530.463614.305580@.i12g2000cwa.googlegr oups.com...

Deadlock between Distribution Agent and Distribution Agent Cleanup

This is occurring regularly on SQL Server 2000 build 878.
The problem is a deadlock in the Distribution database. The Distribution
Agent spid is executing the SELECT statement below:
select @.max_xact_seqno = max(xact_seqno) from MSrepl_commands (READPAST)
where
publisher_database_id = @.publisher_database_id and
command_id = 1 and
type <> -2147483611
which is found in sp_MSget_repl_commands. It holds an Intent Shared page
lock on a data page in the MSrepl_commands table.
The Distribution Agent Cleanup spid is found to be running the command below:
DELETE MSrepl_commands WITH (PAGLOCK) where
publisher_database_id = @.publisher_database_id and
xact_seqno <= @.max_xact_seqno
located in the stored procedure sp_MSdelete_publisherdb_trans. This spid
holds an exclusive page lock on another data page in MSrepl_commands.
Both spids then attempt to obtain the same lock type on the page which is
locked by the other.
The Distribution Agent runs continuously and the Cleanup job is scheduled
for every 10 minutes. The Publication, Distribution and Subscription
databases are all on the same instance (3rd party vendor solution, not mine!)
in an active/active Win2003 cluster configuration. The articles are all
stored procedure executions.
Has anybody else seen this deadlock? Is it just a timing issue? Why is the
PAGLOCK hint used in sp_MSdelete_publisherdb_trans as above?
(I can't find any articles which correlate exactly to this problem)
Kind Regards
Andrew Pike
SQL Server DBA
Accenture UK
Do you have anonymous subscribers or named. With named subscribers the
distribution clean up agent cleans up more aggressively and you may see
problems like this when a subscriber has been offline for some time.
First off issue a select * from distribution.dbo.MSdistribution_status to
see how many undelivered vs delivered commands there are. If there are a
high number of delivered commands, I would stop the SQL Server Agent and run
the distribution clean up agent manually.
I can't comment on why the decision was made to implement the two types of
locks, but in general MS has done a lot of research to deliver optimal
performance. For example the 27 in sp_MSadd_repl_commands27 comes from
tests that they did to find the optimal number of commands to send to the
distribution database in a batch from the log reader agent. And yes, they
tested a range of commands to find which offered best performance.
It looks like the readpast is to prevent locking, and the page lock is to
prevent a table lock.
Hilary Cotter
Looking for a SQL Server replication book?
http://www.nwsu.com/0974973602.html
Looking for a FAQ on Indexing Services/SQL FTS
http://www.indexserverfaq.com
"Andrew Pike" <AndrewPike@.discussions.microsoft.com> wrote in message
news:CFB322D7-1D17-4064-AB36-6338A49C90A4@.microsoft.com...
> This is occurring regularly on SQL Server 2000 build 878.
> The problem is a deadlock in the Distribution database. The Distribution
> Agent spid is executing the SELECT statement below:
> select @.max_xact_seqno = max(xact_seqno) from MSrepl_commands (READPAST)
> where
> publisher_database_id = @.publisher_database_id and
> command_id = 1 and
> type <> -2147483611
> which is found in sp_MSget_repl_commands. It holds an Intent Shared page
> lock on a data page in the MSrepl_commands table.
> The Distribution Agent Cleanup spid is found to be running the command
> below:
> DELETE MSrepl_commands WITH (PAGLOCK) where
> publisher_database_id = @.publisher_database_id and
> xact_seqno <= @.max_xact_seqno
> located in the stored procedure sp_MSdelete_publisherdb_trans. This spid
> holds an exclusive page lock on another data page in MSrepl_commands.
> Both spids then attempt to obtain the same lock type on the page which is
> locked by the other.
> The Distribution Agent runs continuously and the Cleanup job is scheduled
> for every 10 minutes. The Publication, Distribution and Subscription
> databases are all on the same instance (3rd party vendor solution, not
> mine!)
> in an active/active Win2003 cluster configuration. The articles are all
> stored procedure executions.
> Has anybody else seen this deadlock? Is it just a timing issue? Why is
> the
> PAGLOCK hint used in sp_MSdelete_publisherdb_trans as above?
> (I can't find any articles which correlate exactly to this problem)
> Kind Regards
> Andrew Pike
> --
> SQL Server DBA
> Accenture UK
>