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From: Laurenz Albe <laurenz.albe@cybertec.at>
To: Subramanian,Ramachandran <ramachandran.subramanian@alte-leipziger.de>
To: pgsql-novice@lists.postgresql.org <pgsql-novice@lists.postgresql.org>
Subject: Re: AW: AW: AW: AW: Replication Testing- How to introduce a Lag
Date: Mon, 23 Mar 2026 22:59:54 +0100
Message-ID: <89d63402747edb3bf80ff668fdd63cc77334f446.camel@cybertec.at> (raw)
In-Reply-To: <477369bf897b44feb2d2368f6fca93fc@alte-leipziger.de>
References: <aadb9058660d4e10b5cee44b82458802@alte-leipziger.de>
	<f3927bc3a9baf4400325b91652869907f0581c97.camel@cybertec.at>
	<e1e41761323040228570cf6a7e02518e@alte-leipziger.de>
	<8b38fa5141905f9ad6983b8d5ae944e812e3d28a.camel@cybertec.at>
	<fa47fe18078043adbdfe007b7270ffd0@alte-leipziger.de>
	<fc42f77c80fdb3c0267148b807edfacc49b0b0ca.camel@cybertec.at>
	<fc3be1f56ded49dc9be519f92d8b9ab4@alte-leipziger.de>
	<0e00fcc0062b59b88f98dba4900ce49d5a9a3fea.camel@cybertec.at>
	<477369bf897b44feb2d2368f6fca93fc@alte-leipziger.de>

On Mon, 2026-03-23 at 16:36 +0000, Subramanian,Ramachandran wrote:
> I noticed that  RBAs are not incremented one for one . i.e  1 row inserted does not mean RBA=RBA+1 . 1 row updated  does not mean RBA=RBA+1 
> 
> I have ALTER SYSTEM SET recovery_min_apply_delay=300000 ; ( on the stand by side ) 
> 
> On the Source side 
> A simple create table results in a RBA difference of 108328 
> 
> A simple insert of 1 row results in a RBA difference of 296   sometimes 96 
> 
> Is there a way to estimate roughly the amount of data that remains to be transfered ? 

I don't know what an RBA is...

If you are using recovery_min_apply_delay, don't measure the replication lag
with regard to the replay_lsn, because replay is deliberately delayed.
Instead, measure the difference to flush_lsn, the WAL position successfully
transferred to the standby and persisted there.

Yours,
Laurenz Albe





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  Cc: laurenz.albe@cybertec.at, ramachandran.subramanian@alte-leipziger.de, pgsql-novice@lists.postgresql.org
  Subject: Re: AW: AW: AW: AW: Replication Testing- How to introduce a Lag
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