Re: implementing a database log
Date: Tue, 29 Apr 2008 10:08:41 +0100
Message-ID: <slrng1dpcp.rh9.eric_at_tasso.deptj.demon.co.uk>
On 2008-04-29, David BL <davidbl_at_iinet.net.au> wrote:
>
> ....
> Ok so it relates to check pointing. I don't see how these markers are
> particularly useful - ie to determine where to start replaying the log
> during recovery. For example, when ARIES performs a check point it
> records
> 1) the active transaction list
> 2) last LSN (Log Sequence Number) for each active transaction
> 3) the set of dirty pages.
> 4) for each dirty page, the LSN of the earliest log
> record whose effect is not reflected in the page on disk.
>
> This allows the recovery scan to determine where to start replaying
> the log (in the REDO pass).
>
No, I think it's about being able to recover what happened between the last completed checkpoint and the end of the log.
E. Received on Tue Apr 29 2008 - 11:08:41 CEST