Re: Informix beats Oracle

Thanks for the clarification Madison.

I can see where this would be something that needs a little more explaining
to the community, in a presentation of some kind. It appears that this is
going to be useful for high-volume transactions if I'm understanding this
correctly.

Thanks!!

-t-
PS thanks to the rest of you too, DC, Fernando, etc etc.!

Madison Pruet wrote:
Tool wrote:
Well I guess I was thinking this was a bit more than "SET ISOLATION TO DIRTY READ".

What's the difference between that and this new feature? Now I'm totally bamboozled.
Does this mean that in IDS you could not read a locked row at all before this new
feature?

not with committed reads

Or is this just a global dirty-read setting?

No

Dirty Read could return a row which is part of a current transaction and which might be rolled back. Last committed read will only return committed rows. The row might be in the process of being updated or deleted, but the transaction will be returned the last committed version of the row. However, it is always a version of the row which was committed.

M.P.

-t-

Fernando Nunes wrote:
Tool wrote:
Fernando, thanks too for your response. I read your website article and
it was good too.


Thanks!

I have been under the impression that this one feature is what Oracle sells
to clients, that they have the best non-blocking database engine available.
Perhaps this is a bit simplistic, but it is notable that applications and
developers now have another choice of what engine to use if indeed this is
similar to the Oracle implementation, and was not available in other products.

I'm not speaking for IBM... standard disclaimer applies, but:

In practice, I think this has the same results. Using this, you won't block when trying to read a row that has a lock (not a shared one, but an insert/update/delete lock). You will get whatever was there (or wasn't...) before the operation holding the lock.

However, the underlying implementation is AFAIK (I'm not a developer...) completely different. Oracle is a versioned RDBMS like Postgres and I believe some engines used in mySQL. Informix is NOT. The Informix implementation is simpler (quicker?). If it hits a lock, it fetches the value from logical logs.

SQL server has a similar implementation if I read and understood it's documentation correctly (since v2005 if I recall correctly).

From my experience as DBA, this is THE feature that developers were wishing for. From some talks with colleagues and some customers I don't find the degree of enthusiasm I was expecting...

I'll be very happy if my daily customer migrates to IDS 11 and I can use this feature. I'm "tired" of explaining the locking issues to developers that were trained only in Oracle...

It will also make my daily discussions (friendly) with an Oracle DBA much less boring, since we tend to fall in this specific difference :)



.

Relevant Pages

  • Re: Informix beats Oracle
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