Re: Oracle database mirroring questions

You have a lot of good questions below. Thre are several options that Oracle provides. First, you talked about Replication, yes, Oracle has a Replication product for it's database. But, you also asked about mirroring the database to a secondary site(If i understand correctly), that could be done with replication or with 9i DataGuard, basically standby databases. But with 9i, there are three new modes than 8i. Guaranteed, Instant and Delayed(believe this is the 3rd one). With Guaranteed and Instant, changes to your primary database are written instantly to the standby site. Now, you could have multiple standbys and use one or all of them for DR, or, you could use one for offloading query only sessions.

You also mentioned something about clustering/load balancing. Check out 9i RAC, I don't know all the particulars, but, I don't thing you'd be mounting file systems as nfs. With Solaris, I'm guessing the file systems would be raw and have to be concurrent capable. But, with RAC, you only have one set of datafiles, but, multiple SGA's or instances, which goes towards the load balancing. Now, if you're looking for performance and mirroring for DR(Disaster Recovery), you could use 9i RAC and Data guard to do both. RAC is an Extra Cost Option which means you'll be buying EE.

I've setup DataGuard and it's pretty slick, it's much nicer(is that a word) than setting up and maintaining an HAGEO cluster.

HTH,
Pete's

sonyantony_at_hotmail.com (Sony Antony) wrote in message news:<3eb007f1.0304231234.5d190a36_at_posting.google.com>...
> We have been looking at the database redundancy problem from a high
> level for architecturing our distributed application. I m not an
> expert in Oracle. So I decided to ask them here before deciding on any
> particular solution.
>
> 1. Does Oracle provide any database replication/mirroring mechanisms,
> so that there will be a warm backup database to take over, if the
> main/primary crashes. If it does what will be the performance hit (
> cpu usage ) on the primary because this duplication mechanism is
> running in the background.
>
> 2. If such a mechanism as above exists, how does it work. Does it
> duplicate only the modifications of the original database. Does it
> locks the whole tables while it is duplicating the data. Or does it
> lock just the rows - in which case the client applications will not
> 'feel' its presence much
>
> 3. Does Oracle provide any clustering mechanisms for fault tolerance,
> wherein N number of machines will all have exactly mirrored databases.
> One can afford to lose a number of its node machines. As long as at
> least one node is up all client applications can run without any
> problems.
>
> 4. Does Oracle provide any clustering mechanisms for load balancing,
> wherein data will not only duplicated among the nodes as 3. above, but
> different clients can connect to different node machines in a load
> balancing fashion, and they will all see the exact same data.
>
> 5. I was of the understanding that Oracle uses raw disk space. IOW in
> the case of Solaris, it doesn t use the default Solaris UFS file
> system, but uses raw disk space with indexing etc implemented with
> respect to the physical disk location. This makes disk access faster.
> Did I get this wrong. Or is there an option to do it on top of the
> file system or as a raw file system.
>
> 6. One of the possibilities we thought about so as to implement a
> clustering, was to have an NFS server, whose disks are mounted in a
> number of different machines. Each of these machines will run an
> Oracle database server, but accessing the same NFS mounted database.
> Is this possible. I personally didn t think so since if multiple
> machines are modifying the same data at the same time, this will
> result in data corruption, since each machine's modification might not
> be inside a single atomic write() system call.
>
>
> Thanks a lot for reading.
> --sony
Received on Thu Apr 24 2003 - 08:56:42 CDT