One of the most time-consuming aspects of being a DBA is assuring the performance of database systems and applications. A lot of time will be spent on tuning application code and SQL statements to boost efficiency and optimize access. But SQL is only one aspect of database systems performance.
It is also important for DBAs to spend time tuning and optimizing the design, parameters, and physical construction of database objects, specifically tables and indexes, and the files in which their data is stored.
