Undo Tablespaces
Transactions can complete either with a commit or a rollback. A typical transaction ends with a commit, which permanently records the transaction's changes to the database. A rollback undoes all effects of the transaction, as though the transaction never occurred. To provide for transaction rollback, Oracle must keep track of the data that a transaction changes until the transaction commits or rolls back.
Oracle uses a special type of tablespace called an undo tablespace to record rollback data for all transactions. Should you choose to roll back a transaction, Oracle reads the necessary data from the database's undo tablespace to rebuild the data as it existed before the transaction changed it.
Undo Segments
To distribute the ...
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