Oracle will do sorting when executing queries that use ORDER BY, GROUP BY, when a Index is created, and when MERGE SORT is invoked by the SQL optimizer.

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Oracle 9 introduced a new way to manage rollback / undo data – an Undo Tablespace. To utilize Automatic Undo Management, create a tablespace in the database of type UNDO:

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The redo log file holds transaction information. Each Commit causes a flush to the log. You have multiple log files defined – one is “active” or “online”, the others are “offline”. Oracle rotates through these files as each gets full. Switching active files has overhead so the suggestion is that each file can hold roughly 30 minutes or transactions.

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