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doc: Additional information about timeline ID hexadecimal format 

Timeline IDs are sometimes presented to the user in hexadecimal format
(for example in WAL file names).  Add a few bits of information to
clarify this.

Author: Sébastien Lardière <sebastien@lardiere.net>
Discussion: https://www.postgresql.org/message-id/flat/8fef346e-2541-76c3-d768-6536ae052993@lardiere.net
This commit is contained in:
Peter Eisentraut 2023-03-20 08:48:46 +01:00
parent 785f709576
commit 0b51d423e9
2 changed files with 18 additions and 1 deletions
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11
doc/src/sgml/backup.sgml
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@ -1309,7 +1309,16 @@ restore_command = 'cp /mnt/server/archivedir/%f %p'
a new timeline is created to identify the series of WAL records a new timeline is created to identify the series of WAL records
generated after that recovery. The timeline generated after that recovery. The timeline
ID number is part of WAL segment file names so a new timeline does ID number is part of WAL segment file names so a new timeline does
not overwrite the WAL data generated by previous timelines. It is not overwrite the WAL data generated by previous timelines.
For example, in the WAL file name
<filename>0000000100001234000055CD</filename>, the leading
<literal>00000001</literal> is the timeline ID in hexadecimal. (Note that
in other contexts, such as server log messages, timeline IDs are
usually printed in decimal.)
</para>
<para>
It is
in fact possible to archive many different timelines. While that might in fact possible to archive many different timelines. While that might
seem like a useless feature, it's often a lifesaver. Consider the seem like a useless feature, it's often a lifesaver. Consider the
situation where you aren't quite sure what point-in-time to recover to, situation where you aren't quite sure what point-in-time to recover to,

8
doc/src/sgml/config.sgml
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@ -4113,6 +4113,14 @@ restore_command = 'copy "C:\\server\\archivedir\\%f" "%p"' # Windows
a standby server. <literal>latest</literal> is the default. a standby server. <literal>latest</literal> is the default.
</para> </para>
<para>
To specify a timeline ID in hexadecimal (for example, if extracted
from a WAL file name or history file), prefix it with a
<literal>0x</literal>. For instance, if the WAL file name is
<filename>00000011000000A10000004F</filename>, then the timeline ID is
<literal>0x11</literal> (or 17 decimal).
</para>
<para> <para>
You usually only need to set this parameter You usually only need to set this parameter
in complex re-recovery situations, where you need to return to in complex re-recovery situations, where you need to return to