Re: Trouble understanding how to avoid/manage ERROR: multixact "members" limit exceeded

On 8/9/24 03:26, Jim Vanns wrote:
> Hi pggen community!
>
> I am struggling with this error almost daily now and despite various
> efforts, not succeeding in avoiding or dealing with it;

> My questions are;
>
> 1) How should I be managing this? Although not new to PG, I am new to
> this particular problem.
> 2) How can I confirm what processes/tables are contributing to this
> multixact "members" limit?
> 3) What are the units for
> vacuum_multixact_freeze_min_age/vacuum_multixact_freeze_table_age and
> how should I be
>     setting them appropriately for my rates etc.? I can't really find
> anything that explains this clearly.
> 4) How can I check that autovacuum workers are specifically able to
> freeze multixact XIDs and thus avoid this?

pg_stat_activity

https://www.postgresql.org/docs/current/monitoring-stats.html#MONITORING-PG-STAT-ACTIVITY-VIEW

wait_event_type

wait_event

Table 28.12. Wait Events of Type LWLock

This might tell you if something is hanging up on a table or tables.

> 5) Can I check if autovacuum is actually succeeding in its work

pg_stat_all_tables

https://www.postgresql.org/docs/current/monitoring-stats.html#MONITORING-PG-STAT-ALL-TABLES-VIEW

Will show you the vacuum/analyze that has been done on a table.

> Jim Vanns
> Principal Production Engineer
> Industrial Light & Magic, London

--
Adrian Klaver
adrian(dot)klaver(at)aklaver(dot)com