Re: Multixacts wraparound monitoring

Pavlov, Vladimir wrote:
> Yes, VACUUM helps to solve the problem and the WARNING gone away.
> But, the problem is that the VACUUM for the entire database (2.4T) takes over 7 hours, and it has to run every 15-20
hours(about 300 millions transactions), otherwise: 
> ERROR:  multixact "members" limit exceeded - and server stops working.
> The question is how to start the VACUUM at least once in three days.

You should have *started* the thread with this information.

My bet is that your multixacts are overly large and that's causing
excessive vacuuming work; this is likely due to bug #8470 (which is
fixed in 9.5 and master but not 9.3 and 9.4) and my bet is that you
would very much benefit from the patch I posted in
https://www.postgresql.org/message-id/20150620043650.GX133018%40postgresql.org
I didn't actually verify this; you could with some arithmetic on the
deltas in multixact counters in pg_controldata output that you could
take periodically.

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