RE: MultiMaster Replication
- From: "Justin Cave (DDBC)" <jcave@xxxxxxxxxxx>
- To: <fuadar@xxxxxxxxxxxxxx>, <oracle-l@xxxxxxxxxxxxx>
- Date: Wed, 24 Aug 2005 14:25:31 -0600
As Chris mentions, multi-master replication is inherently a tightly
coupled replication solution. As such, it is probably not appropriate
to try to force multi-master replication into the sort of setup you are
describing.
One solution, assuming you are using 9i or later, would be to use
Streams to propagate DML changes between the systems. Streams is
message-based and asynchronous, so it is inherently loosely coupled.
Streams sends a logical change record (LCR) which the destination system
can transform before applying-assuming you wrote the appropriate
transformation routines, you could have one system running v1 of the
schema definition and another system running v2. (Whether this is a
good idea and whether you really want to write the routines to transform
the data going in both directions is another question). I suspect that
it will be a lot easier to fit a Streams-based solution into the
parameters you describe than one based on multi-master replication.
Justin Cave
Distributed Database Consulting, Inc.
http://www.ddbcinc.com/askDDBC
________________________________
From: oracle-l-bounce@xxxxxxxxxxxxx
[mailto:oracle-l-bounce@xxxxxxxxxxxxx] On Behalf Of Marquez, Chris
Sent: Wednesday, August 24, 2005 12:11 PM
To: fuadar@xxxxxxxxxxxxxx; oracle-l@xxxxxxxxxxxxx
Subject: RE: MultiMaster Replication
Not to be negative and not to total disregard your request for technical
help but;
>>4. the business does not want these system to be tightly coupled.
Oracle Multi Master Replication is by definition creating dependences
between to nodes/databases.
They will forever be "tightly coupled" when implementing Oracle Multi
Master Replication
>>5. if the 2 systems are disconnected we might need to change
information on any or both systems.
I have had to "fight" with Oracle Multi Master Replication to "let go"
of replication depends when the Master Def Site was lost.
I tried in vain to drop objects and change the Master Def Site.
Life is definitely better when the two database can talk happily with
each other.
hth
Chris Marquez
Oracle DBA
-----Original Message-----
From: Fuad Arshad [mailto:fuadar@xxxxxxxxx]
Sent: Wed 8/24/2005 9:37 AM
To: Marquez, Chris; oracle-l@xxxxxxxxxxxxx
Subject: RE: MultiMaster Replication
Chris/List
let me try to explain the problem i'm trying to solve.
1. 2 systems same structure intially but software upgrade done
seperately might cause structures not to be in sync.
2. uptime requirements for one node but not the other might cause the
fact that we lose the master definition site(network connectivity)
while the other server is failed over to a hot site.
3. there is transformation happening i.e sequences are different on
both nodes.
4. the business does not want these system to be tightly coupled.
5. if the 2 systems are disconnected we might need to change
information on any or both systems.
"Marquez, Chris" <cmarquez@xxxxxxxxxxxxxxxx> wrote:
>>1....there needs to be a master definition site.
>>if the communication breaks between 2 sites
>>will we have to change the master definition site.
It is possible to change the "master definition site", but generally
this would only be done of the original master definition site is
"gone", "dead", "lost"...temporary loss of one multi-master site does
not mean re-defining the master definition site...unless you need to do
repadmin tasks that must be done for the (down) master definition site.
>>2...replicate sequences
I used local sequence on each side the would *not* collide buy using
different START and INCREMENT values.
I liked Oracle Multi Master Replication for *simple* TABLE level
replication where most or all transaction happen on one node...more than
that and the admin of it (any transaction based replication) becomes
painful.
hth
Chris Marquez
Oracle DBA
-----Original Message-----
From: oracle-l-bounce@xxxxxxxxxxxxx on behalf of Fuad Arshad
Sent: Sun 8/21/2005 10:19 AM
To: oracle-l@xxxxxxxxxxxxx
Subject: MultiMaster Replication
I've been reading up on multimaster replication and had a few questions.
1. After the multimaster replication setup there needs to be a master
definition site. if the communication breaks between 2 sites will we
have to change the master definition site.
2. the tables the i'm trying to replicate have sequences that i need to
transform to sequences on the other side.
oracle seems to say its possbile but i cant find an example.
If anyone on the list has had experience with multimaster. if they
could drop me an email and we could chat a little bit offline that
would be really great.
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