ORA-01555: snapshot too old, When Running Flashback Query

Of all the frustrating, partially-completed features Oracle has released, this is the most frustrating. Did I mention this frustrating feature is frustrating when you get bitten by it?What am I referring to? FLASHBACK QUERY on a table that lives in a database with a large UNDO_RETENTION specified with lots and lots of UNDO_TABLESPACE space. Why is this behaving this way? Silly me, I really should read Oracle docs more carefully.Here’s what they say at Managing Undo for Your Database…There you have it folks. Please don’t get bitten with this the way I did.

OOW09 Diaries: The Week Before

Most of this week I spend in San Francisco — I arrived on Wednesday with couple other Aussie Oracle ACE Directors, Chris Muir and Marcel Kratochvil. This year I have my whole family traveling with me so it should be fun.

Free and Easy Schema diff for Oracle

This post originated from a quick discussion we had internally on how to quickly and easily compare schemas between two Oracle databases. I learned about Sheeri Cabral’s post with a quick comparison solution for MySQL databases and I though of using a similar approach for Oracle. I did some testing and it worked quite well. There certainly are tools in the market, free or not, that do this for us, and even generate scripts to correct differences. The steps below only go as far as to tell you what the differences are. However, they don’t require any additional tool and can be easily executed in any *nix or Windows environment.

Over 4 Billion Buffer Gets?

Recently I was looking into a long-running statement and noticed a curious thing. One moment, I had just over 4 billion buffer gets, and the next I had around 2 million. Beware that if you have had a statement running for some time, you cannot necessarily rely on the buffer_gets column in v$sql—it may be that it has run over the limit, been recycled, and is counting from zero again.

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