Question abt RAC-TAF

All,

We are proposing to implement Oracle 9i RAC for our company's production system for a new OLTP application that is under development.

The question is:
Is it possible to implement RAC on jboss application server?
I guess the answer to it is yes.
But the uncertain thing is: During failover, TAF comes into picture, and the application will be using JDBC thin drivers or OCI for DB connections/connection pooling. I have read in Oracle documentation that connection pooling will not work with TAF.
Barring that, has anyone implemented RAC with JDBC? Or do I need to use OCI drivers?
If yes, can you kindly provide some details about the implementation?

I have also researched on a new driver called C-JDBC, but they have not actually tested on Oracle RAC...

So, if any kind-hearted DBA can provide me something to grab :-) I'll be most grateful.

Thanks in advance.
Suhas

what if TAF?
As far as i'm concern there is nothing to do with jdbc or connection pooling. RAC is where two or more instance running on saperate machine and sharing same storage. During failover your application should look to the other node. This is configurable at jboss at web.xml( if i'm not mistaken).


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Why on earth OCP is to be proud

Quote:

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Originally posted by zainalj
what if TAF?
Why on earth OCP is to be proud

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TAF is Transparent Application Failover

Because OCP might know what TAF is :-)

Well said Julian !
DBAs r supposed 2 know what TAF is !!

I am the DBA for this organization and am not very familiar with front-end like java/asp etc.,

That's the reason I am at a loss as to how application failover happens if the connection drivers (in our case JDBC/OCI) are not compatible... Moreover, TAF does not support DML, another negative..
Still, many advantages can be derived outta RAC, especially for an application like ours, where scalability and availability are priority... We r also considering Data Guard..

Iam keeping my fingers crossed..

Quote:

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Originally posted by julian
TAF is Transparent Application Failover

Because OCP might know what TAF is :-)

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Well, OCM no need to know TAF or whatever product not frequently used. only OCP does. OCP always give comment and complaint on other people said but OCM always trying to help people by answering the given question. So that is why on earth OCM is not to be proud but OCP does. Don't understand???? you must be an OCP.

Hi

For JSP or web application to have failover you need to have your application compiled with correct OCI8 librarries.

The easiest way to demo RAC failover from one node to another is to
use a SQL*Plus session, because it is compiled with the OCI8 libraries, and TAF is pretty straight forward to set up with it.

remember stateful applications cannot be failed over.JDBC thick drivers are okay.(type 2 drivers).I think if my memory doesnt beat me u need to have THICK type drivers only for TAF.think drivers will not work for TAF

TAF has a couple of different failover modes. The default is NONE (i.e. not turned on).

You can also have it set to SESSION (fails over the session but you need to re-execute your last statement), or SELECT (Fail over the session and continue the query).

You can even set it up to have the session PRECONNECT if
you want to. One thing that you can't yet failover is DML, because it's always stateful .

My company had problems becoz of the last one where the customer thought that when we install RAC we are giving him transaction failover..and we had to cancel the contract.

metalink would be your best bet for JDBC driver and RAC certification info.

regards
Hrishy

Hrishy,

Thanks a lot for the informatin that u have provided. I am 100% familiar with the Oracle side (been a DBA for nearly 5 yrs :-)), but I had not had much exposure to application servers...

Anyway, I'll query Oracle on the metalink and hear what they have to say.. Maybe it'll help a lot of implementers having this kinda dilemma...

thanks again :-)

Quote:

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Originally posted by suhasd75
Hrishy,

Thanks a lot for the informatin that u have provided. I am 100% familiar with the Oracle side (been a DBA for nearly 5 yrs :-)), but I had not had much exposure to application servers...

Anyway, I'll query Oracle on the metalink and hear what they have to say.. Maybe it'll help a lot of implementers having this kinda dilemma...

thanks again :-)

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100%?? :-) Really?

We use RAC with PeopleSoft. As PeopleSoft is not TAF aware we can't really use it. Your app has to be coded specficially to be TAF aware.

What we have found though through using server side load balancing is that failover is somewhat transparent to our users. In our config the worst that could happen is that user A submits transaction to server A, server A fails and the APP returns a message like operation failed. If the user submits the same operation again server side load balancing knows enough to direct to the live node and is able to complete the application.

We've been live for a year now and have seen this behavior once in production and thankfully over lunch. It was transaparent enough to the point where I had to tell the managers the next day that we had a failure, they had no idea and we had not one single complaint from any users and we run payroll and portal access for 80,000 users.

Regards,

Steve

Thanks Hrishy and Steve !!

I posted the query in Metalink and got all the information to get me going !! :-)

However, there are still some issues with using JDBC thin and OCI drivers, but it should not stop us from implementing RAC...

Thanks again for everyone's replies... :-)

Do not inplement RAC just for TAF.

TAF is a marketing gimmick which does not work most of the time. Its good only to be used with SQL*PLUS to show demos. Tell me where do u use sqlplus ? Only the DBA and the develpoment team does that and not the end user. Also only select statement works with TAF and not inserts, updates or deletes. Also the sql select TAF is just a replay of the query fired (information is stored about the number of rows that have been thrown to the client and starts throwing after that row). TAF can be implemented on single node databases.

You can use TAF not for Application faliover but for session failovers(to some extent) and login failovers.

You can use the TAF along with OCI to inform you that one of the RAC node is down and you need to restart your application transaction again. Use the OCI call back function to do this.

When one node goes down this error will be thrown "ORA-25402: transaction must roll back". You can then use the OCITransRollback to rollback and restart your trabsaction again.

Remember RACs main purpose is not High Availibility. Its main purpose is scalability and load balancing. Yes High Availibility in the sense that nodes are available but not if the clustered disk system goes down (datafiles).

HTH

Quote:

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Originally posted by adewri
Do not inplement RAC just for TAF.

TAF is a marketing gimmick which does not work most of the time. Its good only to be used with SQL*PLUS to show demos. Tell me where do u use sqlplus ? Only the DBA and the develpoment team does that and not the end user. Also only select statement works with TAF and not inserts, updates or deletes. Also the sql select TAF is just a replay of the query fired (information is stored about the number of rows that have been thrown to the client and starts throwing after that row). TAF can be implemented on single node databases.

You can use TAF not for Application faliover but for session failovers(to some extent) and login failovers.
HTH

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I agree with you here. Even TAF with sql*plus is sketchy. I did OPS and attempted TAF with a HA 311 phone system. I was able to get TAF to work for query failover sometimes and sometimes not in the development stages. As part of the Oracle Contract , Oracle corp sent in a HA specialist to audit my work. He was left scratching is head over why TAF worked sometimes and sometimes not and we was quite throughough in the review of my config.

Quote:

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Originally posted by stmontgo
I agree with you here. Even TAF with sql*plus is sketchy. I did OPS and attempted TAF with a HA 311 phone system. I was able to get TAF to work for query failover sometimes and sometimes not in the development stages. As part of the Oracle Contract , Oracle corp sent in a HA specialist to audit my work. He was left scratching is head over why TAF worked sometimes and sometimes not and we was quite throughough in the review of my config.

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I have almost the same experience.

However, Oracle promised some years ago that TAF will work outside SQL*Plus. Has this been achieved?

Quote:

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Originally posted by adewri
Do not inplement RAC just for TAF.

TAF is a marketing gimmick which does not work most of the time. Its good only to be used with SQL*PLUS to show demos. Tell me where do u use sqlplus ? Only the DBA and the develpoment team does that and not the end user. Also only select statement works with TAF and not inserts, updates or deletes. Also the sql select TAF is just a replay of the query fired (information is stored about the number of rows that have been thrown to the client and starts throwing after that row). TAF can be implemented on single node databases.

You can use TAF not for Application faliover but for session failovers(to some extent) and login failovers.

You can use the TAF along with OCI to inform you that one of the RAC node is down and you need to restart your application transaction again. Use the OCI call back function to do this.

When one node goes down this error will be thrown "ORA-25402:
transaction must roll back". You can then use the OCITransRollback to rollback and restart your trabsaction again.

Remember RACs main purpose is not High Availibility. Its main purpose is scalability and load balancing. Yes High Availibility in the sense that nodes are available but not if the clustered disk system goes down (datafiles).

HTH

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well said..thats perhaphs the reason why DBA's dont make good marketing folks..

I always thought RAC's main purpose was high availability though coz in 10g RAC lotta of emphasis was placed on avalability like ability to do rolling upgrades ..scalability and loadbalancing was always a icing that you got from RAC.

I have been through RAC classes and the general response from the public or atleast 90% of the DBA's was well this is not what i was looking for DataGaurd or Standby database is really what i would be more interested in.

Anyways different folks and different opinions

regards
Hrishy


regards
Hrishy

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Originally posted by hrishy

I always thought RAC's main purpose was high availability though coz in 10g RAC lotta of emphasis was placed on avalability like ability to do rolling upgrades ..

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You can patch a 10g RAC while the DB is up and running in exclusive mode but I don't think this is very attractive as a feature. People always get the dowtime for maintenance..