Which of the following is a common concern regarding data integrity?

Data integrity is fundamentally about the accuracy, consistency, and reliability of data throughout its lifecycle. A common concern in this context is when data does not fall within expected formats. This issue can arise from improper data entry, lack of validation checks, or misinterpretations of data types. When data is not in the expected format, it can lead to processing errors, difficulty in retrieving meaningful information, and flawed analyses, all of which undermine trust in the data's integrity.

In contrast, the other concerns mentioned do not directly address integrity. Frequent changes to data might lead to potential errors or inconsistencies, but they aren't inherently a direct concern of integrity unless those changes are not managed properly. The statements regarding data being always available or never accessible relate to availability, which is a separate aspect of data management known as the availability principle rather than data integrity. Thus, ensuring that data adheres to expected formats is critical for maintaining overall data integrity.