Storage of business data is almost always in the structured storehouse called the relational database. Most software is written to interface with a database server through the SQL language which allows scaling and performance to be manipulated by the more specialized administrator - the DBA. DBA's come in all forms - some from the application angle - others from the server side. The best are those that meld together expertise from both directions that understand the intracacies of the design and performance interdependance.
Since these database servers are the core of applications holding the data, they have become mission critical to the business. Quite often the server is clustered for High Availability in case there is hardware failure taking the critical server down. From Web applications to Data Warehouses - the Database is part of the core services of every IT Dept