Final answer:
The special challenge encountered when many users access and process a database concurrently involves data conflicts, system slowdowns, and a higher chance of errors. Big Data technologies and efficient system design are critical to manage these challenges as seen in large-scale projects like the SDSS and in human factors psychology studies in data-intensive work environments.
Step-by-step explanation:
A special challenge encountered when many users access and process a database is concurrent access and processing. This refers to the condition when multiple users or systems are accessing and manipulating data within a database at the same time, which can lead to a range of issues such as data conflicts, system slowdowns, and increased potential for errors.
In large-scale systems like the Sloan Digital Sky Survey (SDSS), where massive amounts of data are collected and processed—15 terabytes of data, comparable to the information contained in the Library of Congress—Big Data technologies and supercomputers are essential for efficiently handling this volume of information.
Furthermore, studies in human factors psychology like those by Bruno & Abrahão illustrate the impact of cognitive load on decision accuracy in data-intensive environments such as information security centers at financial institutions. This reflects the significant challenges and the importance of considered design in systems that require the processing of vast amounts of data by human operators.