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Question regarding read consistency in Tom Kyte's Expert 10g book

From: <georgejzhang_at_gmail.com>
Date: 5 May 2005 09:57:30 -0700
Message-ID: <1115312250.226306.325880@f14g2000cwb.googlegroups.com>


Hi,

I am reading Chapter one (still beta) of Tom Kyte's new Expert 10g book (http://oracle.apress.com/), and it is really a good read.

However, I have some questions about the read consistency example (page 20 - 22) - getting the total balance of accounts table (I would have tested it if I could). On page 22, table 1-2, what if T7 and T6 interchange their position? If the transaction updates row4 and commits before the query reads row4, the query would not know that row4 has been updated, thus getting the total of 1650? That of course does not sound right. Can you explain how that happens?

And another question, the same example on page 20, why do we assume that the table stores one row per block? What if all 4 row are stored in one block?

Thanks

George Received on Thu May 05 2005 - 11:57:30 CDT

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