Search Postgresql Archives

Re: Determining oldest WAL for Archiving PITR Standby - SOLVED

[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

 



On 17-Oct-07, at 12:01 AM, Brian Wipf wrote:
I'm working on a script that takes backups in intervals from our warm PITR stand by server (both servers running PG 8.2.5). The documentation advises "running pg_controldata on the standby server to inspect the control file and determine the current checkpoint WAL location". I am hoping someone can confirm how to perform this step.

From pg_controldata:
Latest checkpoint location:  8E/624808
Latest checkpoint's TimeLineID:  1
Using the timeline id of 1, log id of 8E and log segment of 0, the oldest WAL needed for a recoverable backup is 000000010000008E00000000

It's not obvious to me why the output in this example doesn't indicate a log segment of 62 and offset of 4808, or a log segment of 6 and offset of 24808.

After watching more output from pg_controldata, I can now answer the question I posted above. (Note: this is for PG 8.2.5. The behavior may be different for other PG versions.)

The offset is the last 6 hex digits of the checkpoint location value. The offset contains leading zeros to make it 6 digits if its actual value is less than 6 digits. Therefore, the digits between the slash and the last 6 digits are the log segment value. If there are no digits between the slash and the last 6 hex digits, the log segment value is simply 0.

If the checkpoint location is 2/3000020 and the timeline id is 1, the corresponding WAL is 000000010000000200000000

Hope this helps,

Brian Wipf
ClickSpace Interactive Inc.
<brian@xxxxxxxxxxxxxx>


---------------------------(end of broadcast)---------------------------
TIP 9: In versions below 8.0, the planner will ignore your desire to
      choose an index scan if your joining column's datatypes do not
      match

[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]
[Index of Archives]     [Postgresql Jobs]     [Postgresql Admin]     [Postgresql Performance]     [Linux Clusters]     [PHP Home]     [PHP on Windows]     [Kernel Newbies]     [PHP Classes]     [PHP Books]     [PHP Databases]     [Postgresql & PHP]     [Yosemite]
  Powered by Linux