Re: oldest xmin is far in the past

Hi,

On 03/18/2016 09:42 AM, John Snow wrote:
> Hi everyone!
>
> Trying to make VACUUM FREEZE on PG instance and keep getting this error:
>
> 2016-03-18 05:56:51 UTC   46750 WARNING:  oldest xmin is far in the past
> 2016-03-18 05:56:51 UTC   46750 HINT:  Close open transactions soon to
> avoid wraparound problems.
> 2016-03-18 05:56:51 UTC   46750 DEBUG:  transaction ID wrap limit is
> 2654342112, limited by database with OID 1
> 2016-03-18 05:56:51 UTC   46750 DEBUG:  MultiXactId wrap limit is
> 2147483648, limited by database with OID 12451
>
> Also "age" and "relfrozenxid" doesnt't change.

That probably means there's an old transaction somewhere - either a 
regular one (check pg_stat_activity) or a prepared one (pg_prepared_xacts).

The meaning of "old" depends on autovacuum_freeze_max_age - what value 
is set in the session running the VACUUM FREEZE?

regards

-- 
Tomas Vondra                  http://www.2ndQuadrant.com
PostgreSQL Development, 24x7 Support, Remote DBA, Training & Services