Monday, February 27, 2006

Getting Burned

The good thing about getting burned once or twice in the forums is you can learn from the experience. For example, the other day somebody wanted to upgrade a 1TB database from 9i to 10g. At the same time, they were changing platforms.

The initial discussion started along the lines of “You should investigate Transportable Tablespaces. I think they are supported across platforms in 10g.” Decent enough idea, I suppose.

Then this particular user chimes in and says:

Db upgrade accross platforms has Exp/Imp as the only option available.

Ah, here’s my chance. Those were my exact sentiments a couple years ago until somebody pointed out you could setup both databases and copy data with a database link. Another person said you could unload/load comma separated data. OK, some maybe not very practical, but still a possibility. Just for the sake of argument, I posted:

100% UNTRUE. You could unload/reload ASCII files, you could use dblinks, you could use Quest's replication product.You should be careful when dealing with absolutes.

OK, maybe a little harsh, but to the point. So Mr. Exp/Imp pipes up and says:

Sure Jeff
Following are excerpts from Metalink doc 277650.1:

The Export and Import utilities are the only method that Oracle supports for moving an existing Oracle database from one hardware platform to another. This includes moving between UNIX and NT systems.

He thinks he as me against the ropes now. If Metalink says it, it must be true. To which I reply:

surprise, surprise, metalink is wrong.

Do I get enjoyment out of proving somebody wrong? Not usually. But there is a lot of bad information out there and I don’t like perpetuating it.


OracleDoc said...

Sounds to me like you were just bored and needed some venting. :p

Jeff Hunter said...

Well, it was Friday night...

Steve Prior said...

Just 2 blog posts ago you were talking about the Oracle Certification and in this post you point out the difference between the correct answer on the certification test and the real world...

OracleDoc said...

LOL @ Steve

Howard J. Rogers said...

So, just to be clear:

Are you saying that Oracle *will* support an upgrade/transport via dblinks or ASCII files, and that Metalink is wrong to say that upgrade/transport via exp/imp is the only supported method of cross-platform movement?

Or are you saying it was wrong in the sense that upgrade/"transport" via dblinks/ASCII files is physically possible?

I just want to be clear on what facts are in dispute here.

Jeff Hunter said...

I'm saying yes on both points. Metalink is wrong to say that upgrade via exp/imp is the only supported upgrade method between platforms. In fact, in the upgrade guide one of the suggested upgrade methods is via dblinks and sqlplus copy. Although I don't work for Oracle Support, I'd suspect they would support a database link across platforms & versions.

Ram said...

Speaking of wrong information, here is one from Datawarehousing guide, 9i, pg 6-3:

"B-tree indexes are most effective for high-cardinality data: that is, for data with _many_ possible values, such as customer_name or phone_number."

Howard J. Rogers said...

I don't particularly wish to prolong the agony, then, but you said in the original post that you had "proved" the other guy wrong. Now you merely "suspect" they would support a database link as an upgrade method.

I see a slight discrepancy there.

You will also, no doubt, recall that Oracle documentation itself suggests moving AUD$ out of the SYSTEM tablespace... and then points out that this is not actually supported. So the fact that dblinks are merely mentioned in the upgrade guide does not of itself prove that they are a *supported* upgrade/transport method.

It's a minor point, but I think you actually have to prove something to be so before you can legitimately blog that you don't usually "get enjoyment out of proving somebody wrong?". Suspicions don't constitute proof.

Jeff Hunter said...

but you said in the original post that you had "proved" the other guy wrong. Now you merely "suspect" they would support a database link as an upgrade method.

Well, I'd disagree with that. The fact that it is in the upgrade guide and isn't specifically labled as "but we don't support it" would imply that it is supported.

Jeff Hunter said...

Just for the sheer sake of argument, I created a TAR. Directly from the TAR:

I want to upgrade a Solaris database to on Red Hat Linux. The database I am upgrading only has 1 table that has about 10000 rows. Because it is so simple, I want to create a database link from the 10.2 database to the 9.2 database and CREATE TABLE t1 AS SELECT * FROM t2@dblink_to_92. Would this method be supported?

Hi Jeff,

This is a supported method. Here the 9.2 database will act as the server and the 10.2 as the c
lient. And 10.2 <--> is a supported combination.

Reference MetaLink note: 207303.1

Sure, ML Note 207303.1 states client/server version interoperability, but in general, yes, it's supported.

Howard J. Rogers said...

I think my point is simply that you were premature to talk about "proving" anything with the OP, when you then had to resort to "imply" and "suggests". The degree of absolute certainty about your position on the matter was not, IMHO, warranted by the known (or stated) facts. As you yourself put it, 'You should be careful when dealing with absolutes'.

That you've now got a statement from support backing your position certainly means your assertion is very much more fact-based than it was. But, unfortunately, we are still left with one quoted Metalink note saying it's not supported and one now being cited as evidence that it *is* supported.

I don't know how you call that, but I still wouldn't say it was black and white "proof" of anything except that support and Metalink can have disagreements amongst themselves and get their positions horribly confused as a result. I'd be interested, for example, in knowing what your Support person would say if you got back to him/her and cited Metalink Note 277650.1. I dare say it would be in Oracle's best interests to be singing the one tune on this one, too!

I think the general point you're making is a perfectly valid one, though: check with Support that they will support you taking a particular path (be it regarding an upgrade or whatever) *before* you take it!

Anonymous said...

Which forum ( could you supply url please ) did the original exchange of views appear in?


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