Re: Autovacuum Transaction Wraparound

Hi Adrian

What was the full message?

autovacuum: VACUUM <table name >(to prevent wraparound)

Though i am running vacuum manually (nowadays) and autovacuum is running
perfectly once its threshold reaches.

What will happen if my DB reaches 200M transaction age again ? ( Here my
understanding is no dead tuples to cleanup --- I may be missing full
concept , Please correct me if i am wrong) .

What will be impact to DB ( Performance ) During Vacuum freeze ( My
Assumption is autovacuum will run "vacuum freeze" once DB age reached 200M
) ?

When should i consider to increase pg_settings value with respect to
Autovacuum ?

Regards,

On Mon, Mar 11, 2019 at 12:45 PM Adrian Klaver <adrian(dot)klaver(at)aklaver(dot)com>
wrote:

> On 3/11/19 12:16 PM, Perumal Raj wrote:
> > Hi Adrian/Joshua
> >
> > Sorry to mention in the previous thread,
> >
> > Auto-vacuum is already enabled in the Cluster and its doing the job
> > perfectly. But only thing manual vacuum scheduled now (weekly Cluster
> > wide) after noticing 'Transaction Wraparound message during Autovacuum
> run.
>
> What was the full message?
>
> >
> > Version : 9.2.24
>
> FYI 9.2 is 1 years+ past EOL.
>
> >
> > Query :
> >
> > SELECT datname, age(datfrozenxid) FROM pg_database
> > datname | age
> > ------------------+-----------
> > template1 | 133492380
> > template0 | 180987489
> > postgres | 93330701
> > nagio | 109936658
> > arch__old | 109936658
> > prod . | 151621905
>
> So at some point the server will force a VACUUM to freeze ids and
> prevent wraparound before the age gets to your autovacuum_freeze_max_age
> below. That might even have been the message you saw.
>
> >
> > Settings :
> >
> > name | setting | unit
> > ---------------------------------+-----------+------
> > autovacuum | on |
> > autovacuum_analyze_scale_factor | 0.05 |
> > autovacuum_analyze_threshold | 50 |
> > autovacuum_freeze_max_age | 200000000 |
> > autovacuum_max_workers | 3 |
> > autovacuum_naptime | 60 | s
> > autovacuum_vacuum_cost_delay | 20 | ms
> > autovacuum_vacuum_cost_limit | -1 |
> > autovacuum_vacuum_scale_factor | 0.2 |
> > autovacuum_vacuum_threshold | 50 |
> >
> > log_autovacuum_min_duration |-1 . |
> >
> > Regards,
> >
> >
> > On Mon, Mar 11, 2019 at 12:07 PM Adrian Klaver
> > <adrian(dot)klaver(at)aklaver(dot)com <mailto:adrian(dot)klaver(at)aklaver(dot)com>> wrote:
> >
> > On 3/11/19 11:51 AM, Perumal Raj wrote:
> > > Hi Experts
> > >
> > > I have noticed in my Database that, there is no regular Vacuum
> > > maintenance happening
> >
> > What Postgres version?
> >
> > > So i started Weekly Job across cluster. But still i am seeing
> > gradual
> > > growth on transacation ID.
> >
> > What query are you using?
> >
> > >
> > > DB is still using default autovacuum_freeze_min_age &
> > > autovacuum_freeze_table_age.
> >
> > What are the actual settings for?:
> >
> > https://www.postgresql.org/docs/10/runtime-config-autovacuum.html
> >
> > >
> > > Question : Since i am running regularly vacuum job ( weekly) and
> the
> > > Transaction age is gradually growing , What is next once i hit
> 200M
> > > limit ( default ).
> > > Should i increase my default value ? If so any calculation for
> > increase
> > > the value based on my DB transaction growth.
> > >
> > > Thanks,
> > > Raj
> >
> >
> > --
> > Adrian Klaver
> > adrian(dot)klaver(at)aklaver(dot)com <mailto:adrian(dot)klaver(at)aklaver(dot)com>
> >
>
>
> --
> Adrian Klaver
> adrian(dot)klaver(at)aklaver(dot)com
>