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Re: WAL -> Replication

From: Hannu Krosing <hannu(at)tm(dot)ee>
To: Curt Sampson <cjs(at)cynic(dot)net>
Cc: Bruce Momjian <pgman(at)candle(dot)pha(dot)pa(dot)us>,Mike Biamonte <mbiamonte(at)affinitysolutions(dot)com>,pgsql-hackers(at)postgresql(dot)org
Subject: Re: WAL -> Replication
Date: 2002-04-26 11:33:30
Message-ID: 1019820810.9449.3.camel@taru.tm.ee (view raw or flat)
Thread:
Lists: pgsql-hackers
On Fri, 2002-04-26 at 07:38, Curt Sampson wrote:
> On Thu, 25 Apr 2002, Bruce Momjian wrote:
> 
> > WAL files are kept only until an fsync(), checkpoint, then reused.
> 
> One could keep them longer though, if one really wanted to.
> 
> > Also, the info is tied to direct locations in the file.  You could do
> > this for hot backup, but it would require quite bit of coding to make it
> > work.
> 
> That's kind of too bad, since log shipping is a very popular method of
> backup and replication.

Now again from my just aquired DB2 knowledge:

DB2 can run in two modes 

1) similar to ours, where logs are reused after checkpoints/commits
allow it.

2) with log archiving: logs are never reused, but when system determines
it no longer needs them, it will hand said log over to archiving process
that will archive it (usually do a backup to some other place and then
delete it). This mode is used when online backup and restore
functionality is desired. This is something that could be interesting
for 24x7 reliability.

-----------------
Hannu



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