Re: Redo log size and standby database

Tim Kearsley wrote:
>
> Hi all,
>
> I've recently taken over responsibility for administration of an OLTP
> database, about 15 Gbytes in size, running Oracle 8.1.7 on AIX 4.3.3.
> Generally, things look in pretty good shape, but one thing I am going
> to need to do in the near future is to create a standby database from
> this live one, to provide at least a read-only facility in the event
> of the live database becoming unavailable, and possibly to provide a
> full failover and activate the standby in the event of real trouble.
>
> My question is this:
>
> The redo logs on the live database are 100 Mbytes, in four groups, no
> multiplexing (just one member per group). Firstly, I'm going to
> mirror the logs and provide at least two members per group. However,
> I'm thinking of reducing the redo log size as log switches seem to
> happen only once per day on average. From what I know about standby
> databases, there is a chance of losing the current log if and when the
> live database becomes unavailable, depending on what causes it to
> become unavailable. In addition, if I remember correctly, there is a
> rule of thumb stating that log switches of a frequency around two per
> hour is a reasonable compromise between short recovery time and
> performance.
>
> Does my reasoning sound, well, reasonable, or are there other factors
> to take into account?
>
> Thanks for any advice and opinions.
>
> Tim Kearsley
> DBA, Milton Keynes Council

Rather than spend hours trying to work out the size that they need to be so that they switch twice per hour, maybe just leave them large and schedule an 'alter system archive log current' every 30 mins

hth
connor

-- 
==============================
Connor McDonald

http://www.oracledba.co.uk

"Some days you're the pigeon, some days you're the statue..."