Oracle Database DR replication and consistency

Posted on 2014-07-29
Medium Priority
Last Modified: 2014-07-30
Hello experts,
I am a quite new DBA with some years experience in IT field and I need your knowledge and help to resolve my issue.

I have a task to plan our future DB architecture which will include projects running with Oracle Databases and SQL Server Databases, and to make it with very good HA and DR levels.

My most important question is:
Which technology or what kind of configuration could I use to achieve Disaster Recovery Site, which could take ownership of the Oracle Databases and SQL Server Databases with minimal downtime and cost?

Both Primary and DR site have SAN - IBM SVC.
The main issue for me is how to achieve Database consistency with async SAN Replication for a low cost or best for the money.

What is known is:
Oracle DB is Standard Edition 11g with possible upgrade to 12c, currently running on Windows Server 2008 R2 EE.
SQL Server is 2008 Enterprise Edition running on Windows Server 2008 EE SP2.

I did quite a lot research and it seems that in order to achieve such DB consistency for Oracle, I have to use DataGuard or GoldenGate, which are separate licenses, and not Options for Standard Edition and for additional cost (quite expensive).
Main Question: Is such thing possible with Oracle Streams when configuring it for whole database replication?

Probably another possibility is to use our license of VMware vSphere 5.5 Enterprise and use the feature Site Recovery Manager, but I saw somewhere that it is paid additional on the count of VMs that could be able to failover.
Is it possible at all, if we virtualize all Oracle instances and datafiles?

Of course, because we have SAN replication, we maybe could use the features of IBM SVC - for example GlobalMirror and achieve Oracle DB consistency. But as I understand it costs additionally every month, something as subscription.

For SQL Server DBs my idea is to use Database Mirroring in async for the DR site.
Question by:Veliko Dragiev
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LVL 122

Accepted Solution

Andrew Hancock (VMware vExpert / EE MVE^2) earned 2000 total points
ID: 40226871
I'll through this in the pot, we have been recently looking at VMware vSphere vSAN for this purpose.

vSAN datastores shared and replicated between ESXi hosts, using 1 x SSD and 1 x Magnetic HDD minimum for the datastore.

the VM is replicated across the vSAN datastore on Hosts, BUT it does depend on your networking for replication, recommended 10GBe.

Author Comment

by:Veliko Dragiev
ID: 40227105
So basically this vSAN is a feature from VMware vSphere 5.5 update 1.
And using it we don't have to use additional IBM Physical SAN replication for the same purpose?

What if we decide to not virtualize Oracle DB servers?
What will help in this case - since DataGuard and GoldenGate are for Oracle Enterprise Edition only?
Could Oracle Streams solve the Replication consistency issue for Hot-Standby between the Sites?
LVL 77

Expert Comment

by:slightwv (䄆 Netminder)
ID: 40227314
Oracle marketing is pushing Real Application Clusters and Dataguard for HA and DR setups.

We are using Streams Replication as long as it lasts (It has been deprecated in 12c.  Oracle is making everyone buy Goldengate!).

Streams Replication is included in Enterprise.  Not sure if it is an 'Option' in Standard.

Looks like Basic Replication is included in Standard:

Not sure what features 'Basic Replication' provides or if it will solve your overall requirement.

As far as Oracle databases and VMWare, you need to be aware of Oracle's Support policy:
Support Position for Oracle Products Running on VMWare Virtualized Environments (Doc ID 249212.1)
What does it mean to be "Always On"?

Is your cloud always on? With an Always On cloud you won't have to worry about downtime for maintenance or software application code updates, ensuring that your bottom line isn't affected.

LVL 35

Expert Comment

ID: 40227452
For an Oracle solution, I don't see why you need Dataguard.  I know they push it, but there certainly isn't a reason that you couldn't script something yourself.

This would only work as a DR solution and not a HA solution.

Essentially set up a secondary log archive destination on the standby server.  Restore a backup to that server, then recover the database until cancel.  Cancel when all logs are applied, then repeat (you only have to repeat the recovery, not the restore).  As long as you never open it, unless you have a disaster, it should be in perfect shape.  Personally, I would make a copy of it and open it to see everything is OK every once in a while, for personal sanity.

If you need the HA ability, you are probably better off with Enterprise Edition.

Author Comment

by:Veliko Dragiev
ID: 40227687
Sounds like an idea, but is this really a hot standby database. Probably with some scripts and so I could achieve that.

For HA, I am going to use Oracle Fail Safe, since we are on Windows Server and we will use the clustering that Windows offers.
For Oracle Standard Edition, RAC is also an option, but it supports a Cluster only of 4 Sockets in total.

Mainly I am interested how to achieve Database consistency, if we replicate the SAN, where the production DB will stay. Of course Oracle Streams does not provide the functionality of automatic failover or something like that to be hot standby, but it could help for the DB consistency I guess.
LVL 35

Expert Comment

ID: 40227805
Yes, it is a physical standby.  However without dataguard, you may have to do some things manually.

I don't believe that the managed recovery mode would be available.  Basically, all you do is:


Essentially do that every day and it won't be that far behind.  You could do it as often as you wanted.  The recover database will essentially stop when it runs out of archives and as long as you don't open it, the database will still be in a state that recovery can continue with the next set of logs.

You need to have checks in place so that you are sure it is progressing through the recovery and no archives are being missed.

Author Closing Comment

by:Veliko Dragiev
ID: 40228508
Seems that from VMware point of view - the first comment could be the solution.

About the physical standby - this is what we have now. But I think this is kind of cold-standby setup.
I am not sure if it is robust enough for Disaster Recovery Site.
I think that Oracle Streams offer the replicated DB to be in read/write state and this could be a benefit when Disaster switchover, because the failover will be only on IP level at DNS...maybe.

Unfortunately Oracle Streams offer only Sync mode for Oracle Standard Edition and there are quite a lot restrictions for using it as DR solution for replication.

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