Final answer:
An implicit commit is not issued when COMMIT; is entered and executed in SQL*Plus; this is actually an example of an explicit commit. Implicit commits occur automatically with certain SQL operations, like DDL statements.
Step-by-step explanation:
The statement that a(n) implicit commit is issued when the user enters and executes COMMIT; in SQL*Plus is false. An implicit commit occurs when certain SQL operations are performed that necessitate a commit to ensure the integrity of the database, such as when a DDL (Data Definition Language) statement like CREATE, ALTER, or DROP is executed. In contrast, the execution of COMMIT; in SQL*Plus is an example of an explicit commit, where the user deliberately instructs the database to save all changes made in the current transaction.