Re: Fwd: Snapshot too old from READ-ONLY table (data pump export)

  • From: Laimutis.Nedzinskas@xxxxxx
  • To: oracle-l@xxxxxxxxxxxxx
  • Date: Tue, 19 Jul 2011 11:36:24 +0300

Since the question was raised again, does anyone know the latest,
up-do-date explanation on how oracle multi versioning works.

ITL's, commit SCN's, row lock byte all put together and explained :)

The problem is that many very clever people reverse engineered one or
another aspect of the process but one can hardly find an all-out
explanation.
I dare to claim that some statements one finds on internet made by even
experienced oracle gurus are doubtful to say the least.
Actually, oracle's own metalink is known to provide hmmm.. strange
statements. That happens.
The whole multi versioning is easy to explain at a high level but
implementation is quite tricky.

Why is implementation that important? Because knowing how it works one can
answer some questions right away how fast oracle can perform in particular
situations.
It's less of a black box approach and more of algorithm analysis then.


Thank you in advance,
Laimis N

--
http://www.freelists.org/webpage/oracle-l


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