Subject: Re: Add A Glossary
To: Robert Haas <robertmhaas@gmail.com>
Cc: Justin Pryzby <pryzby@telsasoft.com>,
 Alvaro Herrera <alvherre@2ndquadrant.com>,
 Corey Huinker <corey.huinker@gmail.com>,
 Roger Harkavy <rogerharkavy@gmail.com>,
 "pgsql-hackers@postgresql.org" <pgsql-hackers@postgresql.org>,
 Fabien COELHO <coelho@cri.ensmp.fr>, Michael Paquier <michael@paquier.xyz>
References: 
 <CADkLM=fwtE-TCU7sRnvaE74z12kOp_A+CdUwMr7aZt39pXbh6A@mail.gmail.com>
 <20200320001122.GA19602@alvherre.pgsql>
 <20200320195841.GA13662@telsasoft.com>
 <CA+TgmoYT2NnUueP5_=Z48XwVpyzciBfNxuuvYKUtLh-korZEmg@mail.gmail.com>
From: =?UTF-8?Q?J=c3=bcrgen_Purtz?= <juergen@purtz.de>
Message-ID: <fbe9b2d9-9f89-83bd-7215-0cc646388ccc@purtz.de>
Date: Tue, 24 Mar 2020 20:40:20 +0100
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On 24.03.20 19:46, Robert Haas wrote:
>> Do we use shared_buffers for WAL ?
> No.

What's about the explanation in 
https://www.postgresql.org/docs/12/runtime-config-wal.html : 
"wal_buffers (integer)    The amount of shared memory used for WAL data 
that has not yet been written to disk. The default setting of -1 selects 
a size equal to 1/32nd (about 3%) of shared_buffers, ... " ? My 
understanding was, that the parameter wal_buffers grabs some of the 
existing shared_buffers for its own purpose. Is this a 
misinterpretation? Are shared_buffers and wal_buffers two different 
shared memory areas?

Kind regards, Jürgen


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    <div class="moz-cite-prefix">On 24.03.20 19:46, Robert Haas wrote:<br>
    </div>
    <blockquote type="cite"
cite="mid:CA+TgmoYT2NnUueP5_=Z48XwVpyzciBfNxuuvYKUtLh-korZEmg@mail.gmail.com">
      <blockquote type="cite" style="color: #000000;">
        <pre class="moz-quote-pre" wrap="">Do we use shared_buffers for WAL ?
</pre>
      </blockquote>
      <pre class="moz-quote-pre" wrap="">No.</pre>
    </blockquote>
    <p>What's about the explanation in
      <a class="moz-txt-link-freetext" href="https://www.postgresql.org/docs/12/runtime-config-wal.html">https://www.postgresql.org/docs/12/runtime-config-wal.html</a> :
      "wal_buffers (integer)    The amount of shared memory used for WAL
      data that has not yet been written to disk. The default setting of
      -1 selects a size equal to 1/32nd (about 3%) of shared_buffers,
      ... " ? My understanding was, that the parameter wal_buffers grabs
      some of the existing shared_buffers for its own purpose. Is this a
      misinterpretation? Are shared_buffers and wal_buffers two
      different shared memory areas?<br>
    </p>
    <p>Kind regards, Jürgen<br>
    </p>
    <p><br>
    </p>
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