Re: Dataguard role switching procedure with active GoldenGate replication - is there a best practice?
- From: Mark Van de Wiel <mark.van.de.wiel@xxxxxxxxx>
- To: "dedba@xxxxxxxxxx" <dedba@xxxxxxxxxx>
- Date: Tue, 18 Sep 2012 21:58:44 -0400
Tony,
First a few questions:
- Are you using GoldenGate just to replicate from 9i to 11g, or are there other
purposes for which you capture the transactions?
- Is C a standby for B (presumably so since you use "active dataguard standby"
which did not exist for 9i)?
- Are you planning downtime during the switch (or at least a read-only state
for a little bit of time)?
- Is A going away, or do you want to keep it around as a 9i backup production
system?
- will B become an active dataguard standby for C?
Assuming you continue to need the GoldenGate replication environment and will
at least stop transactions on A at some point I would recommend:
1) Stop transactions on A.
2) Let extract on A catch up to current and GoldenGate has several ways to find
out whether you are there.
3) Make sure the replicats on B apply all transactions, so that these get
propagated to C.
4) Switch primary and DR between B and C.
5) Configure extract on C to start as of the switch (which is NOW if the
application has not started performing transactions) - otherwise it is as of
the SCN of the switchover which is somewhere in the data dictionary. Configure
datapump and replicats wherever (you can also do this later).
6) Resume processing against C.
Hope this helps.
Mark.
On Sep 18, 2012, at 8:05 AM, De DBA <dedba@xxxxxxxxxx> wrote:
> G'day!
>
> I've got a production database (9i) running on an old server A in the
> "Production" data centre, a new 11g database on server B in the "DR" data
> centre and an active dataguard standby on server C, which is in the
> "Production" data centre. There is a GoldenGate extract and a datapump on
> server A, and 4 GoldenGate Replicats on server B (in "DR"). The plan is to
> migrate the 9i database on server A (Production) to server B (DR) and perform
> a switch so that server C will eventually run production.
>
> The problem that now arises is that due to a change in the project the role
> switch between server B (DR, now primary) and server C (Production, currently
> standby) has to be made whilst replication with GoldenGate is still in place.
> The 4 replicats will therefore need to be moved from server B to server C as
> part of the role switch. As this is a financial system, and the intended
> future production environment, it is unacceptable to loose even one
> transaction in the process.
>
> I was thinking of stopping the datapump extract on server A, noting where it
> left off (trail file, RBA), and allowing the replicats on server B to finish
> applying all trail files that were shipped. Then create a new datapump
> extract to pump to server C, and create new replicats on server C that then
> can start applying with the first trail file they find. This would narrow the
> point of failure to only the datapump, which can be instructed to start
> exactly at the point where the original pump was stopped.
>
> I wonder if this scenario is anywhere near best practice, or indeed whether
> best practices for switching the GG target database over to the standby do
> exist?
>
> Cheers,
> Tony
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>
>
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