Re: Real Application Cluster (RAC) - Access Transperency

Robert Heinzmann wrote:

> Hello,
>
> I'm sorry, maybe I didnt explain my situation well enougth.
>

I'll try to be a bit more explicit .... (and I am open to correction)

In a 2-tier (client server) model or in the last tier of an n-tier, whether the client software is supplied by Oracle or by a third party, it's connectivity is usually through SQL*Net (DB version 7 or earlier), Net8 (DB version 8, 8i) or Oracle Net Services (DB version 9i).

This includes ODBC drivers, JDBC over ODBC, Oracle's supplied JDBC, or any client compiled using Oracle's Pro*, such as Pro*C, or OCI

And anything that uses the Oracle networking layer will use TNSNAMES or one of the enterprise substitutes such as Oracle Names. As a result, what you read about TAF is valid.

(There are a few exceptions. Others in this NG will likely point these out as well as cacth my errors and ommissions. - TIA)

More coments and questions embedded ....

> <snip>
> We have two ways of connecting to a oracle server :
>
> a) Directly with a native interface
> b) throught some kind of oracle supplied client software

Not quite sure what you mean by 'native interface'. Or by oracle supplied client software. And I think the terminology here is what is causing the confusion.

Again - (with very few exceptions) all Oracle supplied clients and Oracle supplied APIs which others use to build their clients communicate to the database through a communications layer known as SQL*Net, Net8 or Oracle Net Services. So basically I see only 1 way to connect to the server. In it's basic form, that layer uses TNSNAMES.ora to provide it's connection directives.

> actually my question comes down to :
>
> Do all client services use tnsnames.ora for client connectivity and thus
> use the HA feature of TAF ?

Yes. (for all practical purposes)

> >
> >
> >>AFAIK (reading the quite bad documentation) the clients have to know
> >>that the Oracle server they connect to is a Oracle RAC server and that
> >>there is a failover node (or more). This configuration is done via the
> >>tnsnames.ora file. What about clients except sqlplus ? they dont use
> >>tnsnames.ora, or do they ? Now do such use the strengthened ability of
> >>the RAC cluster?
> >
> >
> > Minor correction here - all clients that use SQL*Net / Net8 / Oracle Net
> > Services use TNSNAMES.ora or another of the TNS name variants such as an
> > Oracle Names server. And, IIRC, that means all clients (not just
> > SQLPlus), other than some specialized cases of JDBC/RMI.
> >
> > With all due respect, the questions & comments sound almost like you
> > started with the "Real Application Clusters Deployment and Performance" or
> > "Real Application Clusters Setup and Configuration" manuals. If true, I
> > recommend additonal review "Database Concepts" and "Real Application
> > Clusters Concepts", available at
> > http://otn.oracle.com/docs/products/oracle9i/doc_library/release2/nav/docindex.htm.
> >
> > (And yes, there is a technique that needs to be learned to be able to read
> > the manuals.)
>
> Well, acually I started with the "Real Application
> Clusters Concepts" Part 9, which I found in google when looking for for
> an explaination how oracle deals with the transparent access to the
> service.

You might want an even higher level overview. Go to http://otn.oracle.com; under Resources, click on Product Information, then Oracle9i Database, look for Availability.

> We had some customer questions dealing woth oracle RAC and other HA
> cluster solutions. The customer wanted a comparision of a cetain produkt
> with RAC. I was not so familiar with RAC, so I looked for some
> information and found the mentioned "part 9" :)

Failover is usually only part of the requirements. You might also want to review the material at http://otn.oracle.com/deploy/availability/htdocs/ha_features.html#nw_failure for additional ideas.

> generally there are 2 ways to get5 access transperency.
>
> 1) the client know how do deal with it
> 2) there are techniques that make shure access transperency is
> guaranteed (IP Failover with gratitious arp or alike)
>

Look at http://otn.oracle.com/deploy/availability/htdocs/taf.html - perhaps the diagrams will help you with the understanding.

>
> So I was confused how oracle RAC/TAF handles this ?
>
> Most of our customers use any kind of software wih oracle as the databas
> and I dont know how they access Oracle, either by JDBC or Native C++
> Interface (if that is possible :) or any other way. So I wanted to make
> shure if transparent access is guaranteed in any way of client connectivity.
>
> I must say that saying the oracle documention is "BAD" was not ok.
> Generally oracle documentation is good. Technical enougth to get the
> information you need but still keeping a kind of "overview" of the whole
> thing. In this certain case I find the documentation not good. I think
> it is some kind of "marketing material" not dealing with the real
> problem and telling peaople what to expect from TAF. Thats why I said
> that the documentation was bad.
>

It's like looking up a word in the dictionary - if you don't know how to spell the word, finding it is difficult.

Oracle has a lot of information in a lot of documentation, but you have to understand how the document writers have written and organized the material. It takes some effort. Received on Sun Jun 01 2003 - 01:15:08 CDT