問75
頻出度★☆☆
DBMS において，一連の処理が全て成功したら処理結果を確定し，途中で失敗したら処理前の状態に戻す特性をもつものはどれか。
平成30年度 秋期 ITパスポート試験 問75
テクノロジ系データベース › トランザクション処理
This question's explanation and your answers so far.
解説
問 75
Incorrectア
“Index” is an index data structure used to speed up searches on specific columns of a table. Its purpose is to improve the performance of data retrieval, and it has nothing to do with atomicity such as committing or undoing processing.
- イ
正解 イ “Transaction”. A transaction is a single grouping of processing in a DBMS (a logical unit of work). Only when all of the series of operations it contains succeed is the result committed; if even one of them fails partway through, all the processing is undone and the state is restored to that before the processing (rollback). This all-or-nothing property—“either everything succeeds, or it is all treated as if it never happened”—is called atomicity (Atomicity), one of the ACID properties. The wording of the question is precisely a description of this atomicity, so the correct answer is “Transaction”.
Incorrectウ
“Replication” is a mechanism that copies and keeps data on another server or the like, aimed at improving availability and distributing load. It is not a term for the property of committing or rolling back a result depending on whether a series of operations succeeds.
Incorrectエ
“Log” is a record of the processing history. When a failure occurs, the log is used to perform rollback or roll-forward, but the log itself is merely a record, not the property of “committing on full success and reverting to the pre-processing state on failure” itself. The unit that has that property is the transaction.
ここがポイント
- A transaction is an indivisible logical unit of work; on success it commits, and on failure it rolls back to restore the state before processing (all-or-nothing = atomicity, Atomicity).
- The four properties—atomicity, consistency, isolation, and durability—are called the ACID properties of a transaction.
用語