Robert,
Either way, I do believe that you can't have a standby database in both
managed recovery and read only access at the same time which could be your
biggest problem. The application would have to understand that under normal
circumstances it's getting data from database 'X' and during failures from
database 'Y'. This kind of thing gets messy as well. Therefore your best bet
is for local objects that are replicated from elsewhere & since all sites can
update all data your rather stuck. And as far as the network going down, yours
in a similar comment that our network specialist made some 2 years ago, until a
back hoe operator ripped out about 1/4 mile of fiber near our building. Took
the local yokels 4 days to get it repaired. So don't say 'never' as it
definitely can come back to bite you.
Dick Goulet
____________________Reply Separator____________________
Author: "Freeman; Robert " <[EMAIL PROTECTED]>
Date: 3/25/2002 2:52 PM
Thanks for your thoughts Dick! Actually, look into Data Guard in 9i and you
will find that you are no longer constrained by archive log switches!! I'm
really concerned with the conflict resolution issues with MM Replication.
I've done something like this once before, with only 2 sites, but it's been
so long that it's a hazy distant memory. As I recall, the conflict
resolution was a bear.
They are intending on doing the resolution based on a date column and just
saying that the latest date winds... they have a method of keeping the
date/time on the servers in sync as long as the network is up, but my
concern is what happens when it goes down and that date/time sync no longer
is working.... or what happens when the system goes down and they also
replace the hardware and the date/time is not sync'd for several days until
the network is back.
But... then I ask myself how often that will happen too... ;-)
Robert G. Freeman - Oracle8i OCP
Oracle DBA Technical Lead
CSX Midtier Database Administration
The Cigarette Smoking Man: Anyone who can appease a man's conscience can
take his freedom away from him.
-----Original Message-----
Sent: Monday, March 25, 2002 2:37 PM
To: Freeman, Robert ; Multiple recipients of list ORACLE-L
Robert,
Given what you've said it would appear that your only choice is going to
be
symetric/advanced replication, multi-master. The conflict resolution rules
may
be a bear to set up with 5 sites though. Using a standby db would not be
very
effective since data updates are dependent on the archive log switch points
and
that does not address the different sites if your reason for failure is a
network related one. Snapshots won't work either since they are read only.
Dick Goulet
____________________Reply Separator____________________
Author: "Freeman; Robert " <[EMAIL PROTECTED]>
Date: 3/25/2002 9:48 AM
Pretty stringent. They want as little latency as possible. Changes at
a master should be available to all sites ASAP. Now, they could all go
to one central site, and thats ok as long as our networking is healthy,
but if it goes down, there is a requirement that they be able to work
independently (there are 4-5 sites) and then all changes need to be
synchronized. Data loss is secondary to availability however.
These requirements smack of trouble to me.
Robert G. Freeman - Oracle8i OCP
Oracle DBA Technical Lead
CSX Midtier Database Administration
The Cigarette Smoking Man: Anyone who can appease a man's conscience can
take his freedom away from him.
-----Original Message-----
Sent: Monday, March 25, 2002 11:48 AM
To: Multiple recipients of list ORACLE-L
What type of requirement or SLA do you have in regards to keeping the
instances in sync?
-Joe
--- "Freeman, Robert " <[EMAIL PROTECTED]> wrote:
> Stand-by (Oracle9i Data Guard) vs. Replication
>
> Folks,
>
> I have a mission critical system we are architectonic right now.
> There is some argument of the merits of replication vs. using
> Standby database going on.
>
> Current we have 4 sites that we will be replicating data back and
> forth between. There are 3 kinds of data:
>
> 1. Network Critical data (must be available for entire network)
> 2. Regional Critical data (only used for a given region. site =
> region).
> 3. Regional non-critical data (this is data that is easily
> recovered from
> other operational data stores).
>
> I can load you up with details, but for now this is the general
> requirement. We want a given site to be able to work independently
> of the other sites in the event of network failure (WAN).
>
> What I'm looking for is your experience with using replication
> for HA solutions vs. stand-by databases. I've also considered using
> standby databases as a possible solution to this problem, along
> with
> using transportable tablespaces to re-sync the databases once
> everything
> comes up. I'm concerned with replication in that there is allot to
> break,
> and I'm concerned about synchronization issues in general with
> either
> solution.
>
> Thoughts?
>
> RF
>
>
> Robert G. Freeman - Oracle8i OCP
> Oracle DBA Technical Lead
> CSX Midtier Database Administration
>
> The Cigarette Smoking Man: Anyone who can appease a man's
> conscience can
> take his freedom away from him.
>
>
> --
> Please see the official ORACLE-L FAQ: http://www.orafaq.com
> --
> Author: Freeman, Robert
> INET: [EMAIL PROTECTED]
>
> Fat City Network Services -- (858) 538-5051 FAX: (858) 538-5051
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