Re: Max number of WAL files in pg_xlog directory for Postgres 9.2 version

Hi John,

As you said, I have gone through the document. Which one is correct [(2 +
checkpoint_completion_target) * checkpoint_segments + 1 *or*
checkpoint_segments + wal_keep_segments
<https://www.postgresql.org/docs/9.2/static/runtime-config-replication.html#GUC-WAL-KEEP-SEGMENTS>
+
1 files] for 9.2 PostgreSQL?

In my environment we have kept *wal_keep_segments* and *checkpoint_segments*
as below. Will it cause any negative impact?

*checkpoint_segments = 128* # in logfile segments, min 1, 16MB each
#checkpoint_timeout = 5min # range 30s-1h
#checkpoint_completion_target = 0.5 # checkpoint target duration, 0.0 - 1.0
#checkpoint_warning = 30s # 0 disables
*#wal_keep_segments = 0* # in logfile segments, 16MB each; 0 disables

++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++

There will always be at least one WAL segment file, and will normally not
be more than (2 + checkpoint_completion_target) * checkpoint_segments + 1
or checkpoint_segments + wal_keep_segments
<https://www.postgresql.org/docs/9.2/static/runtime-config-replication.html#GUC-WAL-KEEP-SEGMENTS>
+
1 files. Each segment file is normally 16 MB (though this size can be
altered when building the server). You can use this to estimate space
requirements for WAL. Ordinarily, when old log segment files are no longer
needed, they are recycled (renamed to become the next segments in the
numbered sequence). If, due to a short-term peak of log output rate, there
are more than 3 * checkpoint_segments + 1 segment files, the unneeded
segment files will be deleted instead of recycled until the system gets
back under this limit.

++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++

Regards,
Raghavendra Rao

On Wed, 5 Sep 2018 at 23:23, Johnes Castro <johnescm(at)hotmail(dot)com> wrote:

> 1 wal by default occupies 16MB.
> The parameter in version 9.2 that controls this is: wal_keep_segments
>
>
> By setting the parameter to 10, the maximum size of the US pg_xlog will be
> 160MB.
>
> Best Regards,
> Johnes Castro
>
>
> ------------------------------
> *De:* Johnes Castro <johnescm(at)hotmail(dot)com>
> *Enviado:* quarta-feira, 5 de setembro de 2018 15:48
> *Para:* Raghavendra Rao J S V; pgsql-general(at)lists(dot)postgresql(dot)org
> *Assunto:* RE: Max number of WAL files in pg_xlog directory for Postgres
> 9.2 version
>
> Hi,
>
> This page in the documentation can help you.
> https://www.postgresql.org/docs/9.2/static/wal-configuration.html
>
> Best Regards,
> Johnes Castro
> PostgreSQL: Documentation: 9.2: WAL Configuration
> <https://www.postgresql.org/docs/9.2/static/wal-configuration.html>
> 29.4. WAL Configuration. There are several WAL-related configuration
> parameters that affect database performance.This section explains their
> use. Consult Chapter 18 for general information about setting server
> configuration parameters.. Checkpoints are points in the sequence of
> transactions at which it is guaranteed that the heap and index data files
> have been updated with all information ...
> www.postgresql.org
>
> ------------------------------
> *De:* Raghavendra Rao J S V <raghavendrajsv(at)gmail(dot)com>
> *Enviado:* quarta-feira, 5 de setembro de 2018 15:39
> *Para:* pgsql-general(at)lists(dot)postgresql(dot)org
> *Assunto:* Max number of WAL files in pg_xlog directory for Postgres 9.2
> version
>
> Hi All,
>
> We are using postgres 9.2 verstion database.
>
> Please let me know, how many max number of wal files in pg_xlog directory?
>
> What is the formul. I am seeing different formulas. Could you provide me
> which decides number of max WAL files in PG_XLOG directory for Postgres 9.2
> Database,please?
>
>
> --
> Regards,
> Raghavendra Rao J S V
>
>

--
Regards,
Raghavendra Rao J S V
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