Final answer:
Adding structures to improve the performance of database applications is considered an administrative function of the DBMS.
Step-by-step explanation:
Out of the given options, adding structures to improve the performance of database applications is considered an administrative function of the DBMS. This process involves tuning the database by optimizing indexes, tables, and queries to enhance overall performance.
Transaction Support is not an administrative function, but rather a core functionality of a DBMS that ensures data integrity and consistency during multi-step operations.
Web Server Administrative Services and Recovery Services are not administrative functions specific to a DBMS.