Re: pg_xlog error

On 11.07.2011 17:33, jcamera wrote:
> Hi,
>
>     I have problems in my database. I think it is corrupted. Folow my log
> when I tried to start it standalone.
>
> I have some questions:
>
> 1. I saw that the error is in base/30518/449778670_vm file. Can I rebuild
> this file or somethink like this?

*_vm files contain the visibility maps of each relation. Visibility maps 
don't contain any user data, it's just bookkeeping information for 
vacuum to skip parts of tables that don't need vacuuming. They can be 
safely removed, the next vacuum will just take somewhat longer than 
otherwise.

But clearly that error is an indication of corruption, and the 
visibility map probably was not the only thing that got corrupted. It 
looks like you're missing some WAL files, or they got corrupted. It's 
likely that you need to restore from a backup. And you should try to 
figure out what caused the corruption in the first place. Broken 
hardware, perhaps, or fsync=off and a power outage.

> 2. In the last line of log, we can see "DEBUG:  shmem_exit(1): 8 callbacks
> to make". Where can I find these transactions to do callback and/or how can
> I do these callbacks?

That's just an internal debugging line you get when the startup process 
ends. You can ignore it.

--   Heikki Linnakangas  EnterpriseDB   http://www.enterprisedb.com