[sclug] Writing files to 2 places at once?

[Sapan Ganguly]

>
> >         Roland, I didn't build the current Oracle server and I'm not a
> >         DBA so I'm interested in the tablespace replication facilities
>
> Regretably my personal contact with Oracle has been as a developer, not
> as a DBA, so I'm not able to offer specifics, but I'm pretty certain
> that I've seen this done, without dependence upon LVM or similar.


I'll google it. :-)


>          you mentioned.  We have a new DBA, he seems to think that we
> >         only have two options -
> >
> >         1. We take a big downtime hit, shutdown the database copy all
> >         the datafiles across and start up again
> >         2. We do each tablespace seperately, put the tablespace into
> >         backup mode, copy the datafiles across and the apply the redo
> >         logs that build up in the mean time.
> >
> >         Both these solutions will end up with the same amount of
> >         downtime whether it be all in one go or split up over a few
> >         days.
>
> I'm not clear on why the second option involves downtime; will the
> server not process queries while applying redo logs? Even if so, does
> not breaking up the downtime into bite-sized pieces that can be incurred
> over days or weeks at whatever are your lowest load periods not beat
> taking all of the downtime at once?



You may be right, I'm probably being too ambitious, option 2 wouldn't be too
bad.  I guess it will process redo logs while the database it up, I'll check
with the DBA on Monday.

What is the policy for scheduled maintenance windows? If you don't have


[snip]

There isn't one at the moment although management keep talking about "out of
hours" but since we have customers in  almost every time zone and in any
case the data that we collect comes in at an almost constant stream around
the clock.



> In any event, this wasn't what I was proposing. I have the distinct
> (although conceivably mistaken) impression that Oracle is capable of
> maintaining duplicate copies of tablespaces on its own, that you should
> be able to add new tablespaces to a running server and that you should
> be able to alter the constellation of duplicates maintained for a given
> table at will. That said, if your DBA doesn't know to do this, isn't
> confident about it, or indeed, is confident that it's not possible,
> don't try it :-)


It does sound like something that Oracle should be able to do.  I should
maybe try asking the question on an Oracle user group.

Someone else has pointed out that you can get LVM up and running with
> existing volumes with minimal downtime (how long does a server restart
> take you?) and just let LVM fill in the mirror while it's in use. If you
> can work out how to do this, then this may be your best option.


Yeah, Damion suggested that, another thing I try out on the test system.


> You aren't by chance working for a company with a data centre in Whitley
> are you?


Nope, I don't work there.

Sapan
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