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Improve docs for timing and skipping of checkpoints 

Greg Smith
This commit is contained in:
Simon Riggs 2011-11-03 08:52:20 +00:00
parent 7e3bf99baa
commit 4334289186
1 changed files with 9 additions and 2 deletions
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11
doc/src/sgml/wal.sgml
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@ -424,8 +424,15 @@
linkend="guc-checkpoint-segments"> log segments, or every <xref
linkend="guc-checkpoint-timeout"> seconds, whichever comes first.
The default settings are 3 segments and 300 seconds (5 minutes), respectively.
It is also possible to force a checkpoint by using the SQL command
<command>CHECKPOINT</command>.
In cases where there are little or no writes to the WAL, checkpoints will be
skipped even if checkpoint_timeout has passed. At least one new WAL segment
must have been created before an automatic checkpoint occurs. The time
between checkpoints and when new WAL segments are created are not related
in any other way. If file-based WAL shipping is being used and you want to
bound how often files are sent to standby server, to reduce potential data
loss you should adjust archive_timeout parameter rather than the checkpoint
parameters. It is also possible to force a checkpoint by using the SQL
command <command>CHECKPOINT</command>.
</para>
<para>