Tuesday, 30 June 2009

Architecture and Administration Q019

When are the system change numbers assigned?



1. When a transaction begins.
2. When a transaction ends abnormally
3. When a checkpoint occurs.
4. When a commit is issued.



Answer 4 - A system change number or SCN is assigned when the transaction is committed. The SCN is a unique number acting as an internal timestamp and is used for recovery and read-consistent queries.

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