Data and Database Administration Questions and Answers

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.

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.

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.

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.

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.

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.

Answer: A

Correct answer: True

A high-availability system cannot afford the time a restore from backup would take, so it keeps a complete second copy written in step with the first. If one fails the other carries the service immediately. Mirroring guards against media and site failure; it does not guard against a logical error, which is faithfully mirrored too.

Answer: A

Correct answer: True

Backward recovery, or rollback, applies the before-images in reverse order to undo the effects of a transaction that did not complete. It restores the database to the state it held before the transaction began, which is what makes atomicity possible - a transaction either happens entirely or not at all.

Answer: D

Correct answer: The essential data of the record

A transaction log records the essential data of each transaction: its identifier, the time, the type of action, and the data affected. The before and after images of changed records are held in the database change log, which is what a rollback or rollforward actually replays.

Answer: C

Correct answer: Resolve data ownership issues

The distinction is between data administration and database administration. The data administrator is concerned with data as an organisational asset: policy, standards, definitions and who owns which data. Tuning, backup procedures and database security are the technical work of the database administrator.