diff options
Diffstat (limited to 'doc/src')
| -rw-r--r-- | doc/src/sgml/config.sgml | 25 |
1 files changed, 19 insertions, 6 deletions
diff --git a/doc/src/sgml/config.sgml b/doc/src/sgml/config.sgml index 8e2a2c5d736..570c7c3b7de 100644 --- a/doc/src/sgml/config.sgml +++ b/doc/src/sgml/config.sgml @@ -1638,12 +1638,25 @@ SET ENABLE_SEQSCAN TO OFF; </indexterm> <listitem> <para> - The amount of memory used in shared memory for WAL data. The - default is 64 kilobytes (<literal>64kB</>). The setting need only - be large enough to hold the amount of WAL data generated by one - typical transaction, since the data is written out to disk at - every transaction commit. This parameter can only be set at server - start. + 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 <xref linkend="guc-shared-buffers">, but not less + than <literal>64kB</literal> nor more than the size of one WAL + segment, typically <literal>16MB</literal>. This value can be set + manually if the automatic choice is too large or too small, + but any positive value less than <literal>32kB</literal> will be + treated as <literal>32kB</literal>. + This parameter can only be set at server start. + </para> + + <para> + The contents of the WAL buffers are written out to disk at every + transaction commit, so extremely large values are unlikely to + provide a significant benefit. However, setting this value to at + least a few megabytes can improve write performance on a busy + server where many clients are committing at once. The auto-tuning + selected by the default setting of -1 should give reasonable + results in most cases. </para> <para> |