Re: 9i streams vs triggers

"Howard J. Rogers" <howardjr2000_at_yahoo.com.au> wrote in message news:gIGT9.20731$jM5.57174_at_newsfeeds.bigpond.com...
> IMHO, the phrase 'multiversioning' should be reserved for 9i's Workspace
> Management feature, where a table really can have multiple versions of the
> same row physically stored in the same table. But I suspect I'm just
> whistling in the wind here.

I agree with you entirely, multiple versions *of a block's data* doesn't really spark the imagination whereas multiple versions of a logical object (like a table or a view) does. In addition it maybe interesting (or not) to note that a search for 'read-consistent' or read consistency in comp.database.oracle.* returned 723 hits whereas a search for multiversion or multi-version returned 71. So read consistent is probably a better thing to search for in terms of getting valuable information as well.

> Read-consistency means that Oracle knocks up a copy of a block of data and
> rolls it back to a prior time so that you see what the data *used* to look
> like before other people started making changes to it. It's this mechanism
> that means that my writes at 10:03am don't block your read which started
at
> 10.00am and will chug along until 10:30am. When your read at 10:06am
> encounters the block I changed at 10:03, it simply copies the block and
> rolls it back so it looks like it did at 10:00.

This of course is the downside of Tom Kytes excellent dig at non read-consistent databases - that they 'make you wait for the wrong answer', Oracle in contrast merely gives you an out of date answer :(

--
Niall Litchfield
Oracle DBA
Audit Commission UK
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