Re: Database redunancy

You do not have to use Oracle Names for automatic failover, althrough it works. SQL*net or Net8 alone works too. Only thing you have to do is to edit your client tnsnames.ora and make it looks like this:

your_connecting_alias =
(DESCRIPTION =
  (ADDRESS =
(PROTOCOL=TCP)(Host=machine1)(Port=1521))   (ADDRESS =
(PROTOCOL=TCP)(Host=machine2)(Port=1521))   (ADDRESS =
(PROTOCOL=TCP)(Host=machine3)(Port=1521))   (CONNECT_DATA=(SID=your_sid))
)

The sessions of client application will be terminated when instance on machine1 is not available. New sessions will automatically switch to instance on machine2. Note that the above requires you have same sid on different machines. This configuration is designed for OPS and Symetric replication. Hope it works for you.

By the way, on the application side, it can be done similiarly.

Rcihard Yin
Oracle DBA & UNIX SA
Sprint

In article <ubQ94.3250$VY5.17570_at_news.uswest.net>,   "W. Scott Moore" <sirws_at_hotmail.com> wrote:
> You can also centralize your tnsnames.ora file and add the tns_admin
> registry key to point to the centralized tnsnames.ora on all of the
client
> machines.
>
> That way, when you need to switch the machine that is being pointed
to, you
> can just edit the main tnsnames file that would be on a fileserver
> somewhere.
>
> Does that make any sense?
>
> In case you don't know, the tnsnames.ora is usually put in the
> orahome\net80\admin directory, and you can override this by adding the
> tns_admin string value in the
> [HKEY_LOCAL_MACHINE\SOFTWARE\ORACLE] key.
>
> Should look something like:
>
> [HKEY_LOCAL_MACHINE\SOFTWARE\ORACLE]
> "TNS_ADMIN"="d:\\temp"
>
> where d:\temp could be your network fileserver.
>
> Anyway, that is just a thought I had. Hope it helps.
>
> Scott
>
> "Kenneth C Stahl" <BlueSax_at_Unforgettable.com> wrote in message
> news:3862258B.29F24895_at_Unforgettable.com...
> > I have been asked to investigate the possability of setting up a
> > fault-tolerant Oracle instance on a Sun 450/SunOS5.6 system. The
> > requirements are somewhat fuzzy, but maybe someone will recognize
what I'm
> > trying to accomplish.
> >
> > The system architects want to set up the file system so that it is
> mirrored
> > to another file system. They would like to have Oracle set up so
that if
> > the primary database fails that another instance will be instantly
> > available which uses the mirrored files.
> >
> > In a way this seems to be backwards from parallel server since that
schema
> > would use two different instances against the same files. In my case
it
> > would be an instance with the same name as the primary instance
except
> that
> > it would be running on another machine (in a cluster configuration).
> >
> > I do see some tremendous problems with this since all of the
applications
> > programs are actually running on NT workstations as client
applications.
> > Even if I could do the database end I don't see how I could
instantly
> > switch users over to the alternate instance without diddling with
the
> > tnsnames.ora. If it were simply a matter of having them log in
different
> by
> > specifying a difference database alias I could see how that could be
> > handled, but I didn't write the login screens and the database alias
is
> > hardcoded into one of the programs and is handled by a global
configurator
> > for the other applications. Considering that the current usages is
about
> > 80-100 call-center agents, it would appear to me that the deck is
stacked
> > against me for any type of automated switchover.
> >
> > So, that is the background. Any thoughts?
>
>

Sent via Deja.com http://www.deja.com/
Before you buy. Received on Tue Dec 28 1999 - 00:20:39 CST