Answers in-line
Regards
Jonathan Lewis
http://www.jlcomp.demon.co.uk
The educated person is not the person
who can answer the questions, but the
person who can question the answers -- T. Schick Jr
One-day tutorials:
http://www.jlcomp.demon.co.uk/tutorial.html
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UK___November
The Co-operative Oracle Users' FAQ
http://www.jlcomp.demon.co.uk/faq/ind_faq.html
- Original Message -
To: Multiple recipients of list ORACLE-L [EMAIL PROTECTED]
Sent: Wednesday, December 24, 2003 9:44 PM
It's been awhile since I've looked at flashback queries, and
I have a couple questions:
* Given an SCN, is there any way to know for certain whether
a flashback query to that SCN is possible? Can a non-DBA
user determine this?
No, not without doing it.
As a general principle, you can always be in a position where
one querycan flash back to SCN = t1, but another query can't
because the two queries require undo from different segments.
* Is there an easy way to determine how much undo data my
database is (hopefully) retaining? In other words, can I
easily determine how far back in the past I *can* go?
No.
You could mess about with dumping segment header blocks
and looking at the 'retention' table, which has a timestamp
per extent of the most recent commit recorded against that
extent. The highest (most recent) timestamp would be a
valid bound for the earliest point in time that you could
reach - but depending on luck, size of extents, etc. you
might get some queries going a lot further back.
Yes, here it is Christmas eve, and I'm working away...
Best regards,
Jonathan Gennick --- Brighten the corner where you are
http://Gennick.com * 906.387.1698 * mailto:[EMAIL PROTECTED]
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