問53
頻出度★☆☆
データベース管理システムを利用する目的はどれか。
平成23年度 秋期 ITパスポート試験 問53
テクノロジ系データベース › データベース方式
This question's explanation and your answers so far.
解説
問 53
Incorrectア
A DBMS is middleware that runs on top of an OS (software positioned between applications and the OS), and it relies on the OS for basic functions such as file read/write, memory management, and process management. So the statement that it makes data usable even without an OS does not hold. On the contrary, the DBMS itself is the side that runs by using OS services; it is not a replacement for the OS.
Incorrectイ
A DBMS does provide recovery functions that use backup files and logs (journals), and it helps you recover from failures, but only on the premise that backups are taken regularly. In a media failure where the disk itself breaks, recovery follows the steps of restoring from a backup and then applying the log (roll forward), so backups never become unnecessary. RAID and duplication, which raise availability, are measures used together with backups; neither of them replaces a backup.
Incorrectウ
Encrypting data that is sent and received over a network is the role of communication protocols such as SSL/TLS, or of a VPN; it is not the original purpose of a DBMS. Some recent products do offer optional features that encrypt the communication channel or the stored data, but those are only supplementary security functions, and they are a different matter from the DBMS's own purpose of managing data centrally and sharing it while keeping it consistent.
- エ
正解 The correct answer is “エ Allow multiple users to share information while ensuring data consistency.” A DBMS (Database Management System) is software that manages data centrally so that many users and applications can use it together, resolving the duplication and inconsistency that arise when each business task keeps its data in its own separate files. When data is used at the same time, inconsistency can occur: for example, if two people read the same stock quantity and each of them updates it, one of the updates disappears (lost update). The DBMS therefore coordinates simultaneous updates to the same data with locking (exclusive control), and with transaction management it makes a series of operations either fully applied or fully cancelled (commit / rollback); when a failure happens it uses the log to recover a state with no contradictions. It also checks integrity constraints on the data (primary key uniqueness, referential integrity, and so on) and sets access rights for each user, which prevents incorrect data from being registered and blocks unauthorized access. Achieving a state where “everyone can use the same data without contradictions” through such mechanisms is the purpose of using a DBMS.
ここがポイント
- The purpose of a DBMS (Database Management System) is to manage data centrally so that multiple users and applications can share it, while preventing duplication and contradiction in the data and keeping it consistent (maintaining integrity). This is supported by functions such as locking (exclusive control), transaction management (commit / rollback), integrity constraints, access-rights management, and failure recovery using logs and backups.
- Separate the confusing options by which layer is responsible. Hardware resources and file management belong to the OS, encryption of the communication channel belongs to network functions such as SSL/TLS, and preparing for media failure belongs to operational measures such as backups and RAID; the DBMS is the middleware that sits above them and takes charge of sharing data and keeping it consistent. Memorize it organized in this layered way.
用語