Dan, My understanding of a TTS is that we write the
highest SCN to header (just like we do with any
tablespace) of the TTS when it is made read only.
After the TTS is transported we then look at the SCNs
like we do in a distributed transaction environment
and we will bump the SCN in the current database if it
is lower than the TTS SCN. The blocks then should be
cleaned out accordingly when selected.
My best guess without testing,
Scott
- Daniel Fink <Daniel.Fink_at_Sun.COM> wrote:
> This is not in response to an actual problem, it is
> just the
> result of a brain that goes off on tangents way to
> often...
>
> How does a transaction know NOT to build a
> consistent version of
> data that has been transported?
>
> Sequence of events
> 1) Insert records into table1. A Commit SCN of
> 100000 is
> assigned. Due to the size of the insert, there are
> blocks in the
> table that still have an Uncommitted state.
> 2) Alter tablespace1 (containing table1) to read
> only and
> transport it to database2.
> 3) Start a query in database2 (with an SCN of 1000)
> that
> accesses the newly transported table1.
>
> Will the query get a 1555?
>
> Yes - It cannot create a read consistent view to SCN
> 1000
> No - It knows that this data came from another
> database, so it
> does not attempt to build a read-consistent version
>
> Thoughts on which is correct? I know, I know...build
> a damn
> testcase and see for myself. I'm working on it, but
> I wanted to
> see what you all thought first.
>
> Daniel
>
>
>
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Received on Fri Mar 19 2004 - 19:06:31 CST
