Обсуждение: Number of WAL segment

Hi,
I am using PostgreSQL 8.3.8!!!
How can I increase number of WAL segments in pg_xlog???
Current settings are:
checkpoint_segments=10
checkpoint_completion_target=0.5

WAL segments are generated every 10 min and I want to keep WAL segments in
pg_xlog for at least 3h.

Thanks...




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Hi,

(13/09/17 21:46), tdev457 wrote:
> Hi,
> I am using PostgreSQL 8.3.8!!!
> How can I increase number of WAL segments in pg_xlog???
> Current settings are:
> checkpoint_segments=10
> checkpoint_completion_target=0.5
>
> WAL segments are generated every 10 min and I want to keep WAL segments in
> pg_xlog for at least 3h.

In 8.3, the number of wal segments can not be controlled explicitly.
# If you can use version 9.0 or higher,  please see here:
#
http://www.postgresql.org/docs/9.3/static/runtime-config-replication.html#GUC-WAL-KEEP-SEGMENTS

In any case, It is not possible to control the retention period.
I recommend WAL Archiving, if you want to save 3 hour's wal segments
with certainty.

Regards,

Thanks,
I am confused now.When checkpoint_segment is set to 3 there are 7 WAL
segments in pg_xlog.When I set checkpoint_segments to 10 there are 11 WAL
segments.




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On Tue, Sep 17, 2013 at 2:35 PM, tdev457 <idzob23@gmail.com> wrote:
> Thanks,
> I am confused now.When checkpoint_segment is set to 3 there are 7 WAL
> segments in pg_xlog.When I set checkpoint_segments to 10 there are 11 WAL
> segments.
The maximum number of WAL files is defined by this formula:
(2 + checkpoint_completion_target) * checkpoint_segments + 1
http://www.postgresql.org/docs/8.3/static/wal-configuration.html
Note that this is a soft limit, there could be more than 3 *
checkpoint_segments + 1 for a short period.
--
Michael

On Tue, Sep 17, 2013 at 9:46 PM, tdev457 <idzob23@gmail.com> wrote:
> Hi,
> I am using PostgreSQL 8.3.8!!!
> How can I increase number of WAL segments in pg_xlog???
> Current settings are:
> checkpoint_segments=10
> checkpoint_completion_target=0.5
>
> WAL segments are generated every 10 min and I want to keep WAL segments in
> pg_xlog for at least 3h.
It is not possible to keep WAL files in pg_xlog in 8.3 for such a
duration as checkpoint_timeout would kick a checkpoint at least every
hour even if you'd set it to its maximum value which is 1 hour. So the
solution to keep 3 hours of WAL files in this case is simply to use an
archive, and to delete periodically old files no longer needed based
on your needs.

Note that you could use wal_keep_segments with a server >= 9.1 to do that.
--
Michael