8.3. Summary
In this chapter, we presented the undo tablespace and its importance for the two types of database users: those who want to query a table and receive consistent results, and those who want to make changes to a table and have the option to roll back the data to its state when the transaction started. The undo tablespace provides undo information, or the value of rows in a table before changes were made, for both classes of users. More specifically, undo data facilitates rollback operations, read consistency, certain database recovery operations, and several types of flashback features, some of which were introduced in Oracle9i and greatly expanded in Oracle 10g.
An undo tablespace can be configured with a handful of initialization ...
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