Re: changelog deadlock replication failures with DNA

[Rich Megginson <rmeggins@xxxxxxxxxx>]

On 06/18/2013 01:51 AM, thierry bordaz wrote:

On 06/18/2013 12:35 AM, Mahadevan, Venkat wrote:

I do not know why your environment is prone to trigger db_deadlock (lot of replica agreements, VM, slow disks...).
I think the best way to progress is that you fill a ticket/bug so that we may track the issue. Note this bug is possibly affecting all operations (ADD/MOD/MODRDN/DEL)

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Hi Thierry,

 

We are running in a VMWare environment, is this known to cause issues and are there any tuning steps you can recommend or things

to watch out for? Thanks and sorry for so many questions.

 

cheers,

 

VM

Hi Mahadevan,

Running in a VM should not be an issue if it follows the usual tuning recommendation. But of course it adds a layer when investigating a RC.
What is weird is to hit so frequent (50) deadlock in a single DB call. In addition it looks like it always happen when updating the CL so I can think to only RA threads, CL trimming and Write thread (the one holding the backend lock) being in competition.

Search threads also.  Searches acquire a read lock on the pages used by the entry and the indexes.

You may try to disable the RA for a test to check if they are responsible of that. You may also remove the CL maxage to prevent the CL trimming thread to be in the loop. Also you may check if you have pb with disk IO. Or tune the dbcache to be in memory.
Sorry I have no easy answer to your question because it requires deeper investigations.

best regards
thierry

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