Re: Solution for 01555

"vlad" <bulk_at_sfatcu.com> wrote in message news:<ZHpX9.84110$1q3.16415_at_sccrnsc01>...

Yikes! Can you folks trim the quoting of previous posts?

> Hey, the question about flashback is completely unfair. That's not something
> a database is required to support. It's one those cool things you can do
> with Oracle. A database is not supposed to give you the history or the
> future of a record. It IS, howewer, supposed to tell me what's in the table
> right now without giving me some "snapshot error". I'm asking a fair
> question, and I should get an answer.

Debatable. Flashback was actually a "nice to have" from user requests, not Oracle trying to force it on any1. As for "what's in the table right now", there has been more debate about that since databases started (yes, even in old hierarchical databases that problem was already present!) than any other aspect of this technology. Rolback (or redo) is not a new concept: it's been around since the early 70's.

>
> Now, I understand, that given the time and resource limitations we all live
> under, Oracle maybe couldn't do all this and still charge a reasonable price
> for its software. Still, an architecture liable to abstruse errors like
> "delayed block cleanout" simply sounds incomplete to me.

Actually, I think you got this wrong. The rollback read-consistency model has been in Oracle since V3. That's about 1983 or thereabouts. It's of course been improved and made many times more efficient since then, but it's not a haphazard new concept that just made the light of day with 9i. No matter how much you may have read about it in Oracle's marketing pamphlets.

1555 is NOT a new error. Been there since I can remember working with Oracle. The delayed block cleanout as a cause of it is, however, a consequence of a new way of handling blocks in cache that came in V7. IIRC. All this to say: it's not a new concept, subject to polishing. It's been thought out very well and it works exceedingly well at providing an architecture where writers NEVER EVER block readers, something that no other RDBMS in the market at the moment can provide, AFAIK. That is good.

Cheers
Nuno Souto
nsouto_at_optushome.com.au Received on Thu Jan 23 2003 - 20:30:44 CST