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Questions and Answers
What is undo data primarily used for?
What is undo data primarily used for?
Undo data is retained only until the transaction is completed.
Undo data is retained only until the transaction is completed.
False
What action would cause a user to roll back a transaction?
What action would cause a user to roll back a transaction?
User undoes a transaction.
Undo information is stored in ______ segments.
Undo information is stored in ______ segments.
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Which of the following statements is TRUE regarding undo tablespaces?
Which of the following statements is TRUE regarding undo tablespaces?
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The UNDO_RETENTION parameter determines how long undo data is retained for committed transactions.
The UNDO_RETENTION parameter determines how long undo data is retained for committed transactions.
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Name one function of undo data.
Name one function of undo data.
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Match the following actions with their triggers for undo data retention:
Match the following actions with their triggers for undo data retention:
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Study Notes
Undo Data
- Undo data is a record of transactions that change data.
- Undo data is captured for every transaction.
- Undo data is retained at least until the transaction ends.
- Undo data is used to rollback operations.
- Undo data is used to support Read-consistent queries.
- Undo data is used to support Oracle Flashback Query, Oracle Flashback Transaction, and Oracle Flashback Table.
- Undo data is used to recover from failed transactions.
Storing Undo Information
- Undo information is stored in undo segments.
- Undo segments are located in undo tablespaces.
- Undo tablespaces are used only for undo segments.
- Undo tablespaces have special recovery considerations.
- Undo tablespaces can be associated with a single instance.
- Only one undo tablespace can be the current writable undo tablespace for a given instance.
Comparing Undo Data and Redo Data
Managing Undo
- Automatic undo management automates managing undo data and space.
- Automatic undo management uses a dedicated undo tablespace.
- Automatic undo management self-tunes in AUTOEXTEND tablespaces to satisfy long-running queries.
- Automatic undo management self-tunes in fixed-size tablespaces for best retention.
DBA Tasks
- DBAs must configure retention settings for undo data.
- DBAs can change undo tablespaces to a fixed size to avoid space and "snapshot too old" errors.
- The UNDO_RETENTION parameter specifies how long already committed undo information is retained.
Configuring Undo Retention
- Set the UNDO_RETENTION parameter when the undo tablespace has AUTOEXTEND enabled.
- Set the UNDO_RETENTION parameter to configure undo retention for LOBs.
- Set the UNDO_RETENTION parameter to guarantee undo retention.
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Description
This quiz covers the concepts of undo data in Oracle databases, including its role in transaction management and recovery. Explore how undo segments and tablespaces function, as well as the differences between undo and redo data. Test your understanding of automatic undo management and its significance.
