Incorrect data is easy to detect.
Answer: B
Correct answer: False
Incorrect data is usually well-formed and plausible - a valid date that is the wrong date, a real address belonging to someone else - so it passes every format check and is discovered only when someone acts on it. This is why quality has to be built in at the point of capture rather than inspected for afterwards.
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Poor data administration can lead to which of the following?
Answer: C
Correct answer: Missing data elements
Poor data administration shows itself in missing data elements and in the same entity being defined several different ways in different systems. A single definition of an entity and familiarity with the existing data are what good administration produces, so those two cannot be its failures.
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Backward recovery is which of the following?
Answer: A
Correct answer: Where the before-images are applied to the database
Backward recovery is rollback: the before-images from the log are written back, undoing the transaction’s changes and returning the database to its earlier state. Forward recovery starts from a backup and applies the after-images to bring it up to date.
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A shared lock allows which of the following types of transactions to occur?
Answer: C
Correct answer: Read
A shared lock permits reading, and several transactions may hold one on the same item at the same time - reads do not interfere with each other. Any change requires an exclusive lock, which no other transaction may hold in any mode.
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Information repositories are replacing data dictionaries in many organizations.
Answer: A
Correct answer: True
A data dictionary describes the database; an information repository describes the whole information landscape - data models, processes, applications, users, and the relationships between them. As organisations came to need lineage and impact analysis across systems, the wider tool displaced the narrower one.
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Which of the following is true concerning open-source DBMS?
Answer: A
Correct answer: Is free or nearly free database software whose source code is publicly available
Open-source means the source code is published and may be inspected, modified and redistributed, and the software is generally free or nearly so. MySQL and PostgreSQL are the familiar database examples, and both are competitive with commercial products and substantially SQL compliant.
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Which of the following is the preferred way to recover a database after a transaction in progress terminates abnormally?
Answer: A
Correct answer: Rollback
When a single transaction fails part way through, only that transaction’s work needs undoing - so the system applies the before-images from the log and rolls it back. Nothing else in the database is affected, which is why this is far cheaper than any of the alternatives.
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A data warehouse administrator is concerned with which of the following?
Answer: B
Correct answer: The time to make a decision and the typical roles of a database administrator
A data warehouse administrator does everything a database administrator does - storage, backup, tuning, security - and is additionally judged on how fast the warehouse can answer a question, since its whole purpose is to support decisions. A warehouse that is correct but slow has failed at its job.
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Queries that do full table scans should be avoided.
Answer: A
Correct answer: True
A full table scan reads every row, so its cost grows with the table rather than with the answer, and on a large table it also displaces useful pages from the buffer. Ordinarily an index should be available and used. The qualification is that a scan is genuinely cheaper when a query touches most of the rows anyway.
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Authorization tables contain highly sensitive data and should be protected by stringent security rules.
Answer: A
Correct answer: True
An authorization table records who may do what, so anyone able to read it learns where the valuable data lies, and anyone able to alter it can grant themselves whatever rights they wish. It is therefore among the most sensitive objects in the database and is protected more strictly than the data it governs.
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