You work as a database administrator for TCS .com. The UNDO_RETENTION parameter in your database is set to 1000 and undoretention is not guaranteed. Which statement regarding retention of undo data is correct?
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Undo data becomes obsolete after 1,000 seconds.
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Undo data gets refreshed after 1,000 seconds.
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Undo data will be stored permanently after 1,000 seconds.
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Committed undo data would be retained for 1,000 seconds if free undo space is available.
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Undo data will be retained in the UNDOtablespacefor 1,000 seconds, then it gets movedmovedto the TEMPORARY tablespace to provide read consistency.
When UNDO_RETENTION is set to 1000 and retention is not guaranteed, Oracle attempts to retain committed undo data for 1000 seconds IF sufficient free undo space exists. Option D correctly states this. Option A is incorrect because undo doesn't become obsolete exactly at 1000 seconds - it stays longer if space permits. Option B is wrong because undo isn't refreshed. Option C is incorrect because undo isn't stored permanently. Option E is wrong - undo never moves to TEMPORARY tablespace.
To answer this question, we need to understand the concept of the UNDO_RETENTION parameter and its effect on the retention of undo data in a database.
The UNDO_RETENTION parameter is used to specify the minimum amount of time (in seconds) that Oracle should attempt to retain undo data before it is overwritten. It does not guarantee the retention of undo data for the specified duration; rather, it provides a target for Oracle to aim for.
Option A) Undo data becomes obsolete after 1,000 seconds. This option is incorrect. The UNDO_RETENTION parameter does not make the undo data obsolete after a specific duration. It only sets a target retention time.
Option B) Undo data gets refreshed after 1,000 seconds. This option is incorrect. The UNDO_RETENTION parameter does not refresh the undo data after a specific duration. It only sets a target retention time.
Option C) Undo data will be stored permanently after 1,000 seconds. This option is incorrect. The UNDO_RETENTION parameter does not store undo data permanently. It only sets a target retention time.
Option D) Committed undo data would be retained for 1,000 seconds if free undo space is available. This option is correct. When the UNDO_RETENTION parameter is set, committed undo data will be retained for the specified duration if there is enough free undo space available. If free undo space is not available, then the oldest undo data may be overwritten.
Option E) Undo data will be retained in the UNDO tablespace for 1,000 seconds, then it gets moved to the TEMPORARY tablespace to provide read consistency. This option is incorrect. The UNDO_RETENTION parameter does not involve moving undo data to the TEMPORARY tablespace. The UNDO tablespace is specifically used to store undo data.
Therefore, the correct answer is Option D. Committed undo data would be retained for 1,000 seconds if free undo space is available.