Sufficient capacity

A database's primary function is to store large amounts of information. For example, an order management system for a medium-sized company can easily grow into gigabytes of data; the bigger the company, the more data it needs to store and rely upon. A company that wants to keep historical (archival) data will require even more storage space. The need for storage capacity is growing rapidly, and databases provide for structured storage.

Adequate security

As was noted previously, enterprise data is valuable and must be stored safely. That means protection of the stored data not only from malicious or careless human activities, such as unauthorized logins, accidental information deletions/modifications, and so on, but also from hardware failures and natural disasters.

Multiuser environment

It's also important to note that in order to be useful, the information stored in a database must be accessible to many users simultaneously at different levels of security, and, no matter what, the data must stay consistent. For example, if two users try to change the same piece of information at the same time, the result can be unpredictable (e.g., data corruption), so situations like that have to be handled appropriately by internal database mechanisms. Also, certain groups of users may be allowed to modify several pieces of information, browse other parts of it, and be prevented from even viewing yet another part. (Some company data can be strictly confidential with a very restricted access.)

Effectiveness

Users need quick access to the data they want. It is very important not only to be able to store data, but also to have efficient algorithms to work with it. For example, it would be unacceptable for users to have to scroll through each and every record to find just one order among millions stored in the database; the response to someone's querying the database must be fast, preferably instantaneous.

Scalability

Databases must be flexible and easily adaptable to changing business needs. That primarily means that the internal structure of database objects should be easily modified with minimum impact on other objects and processes; for example, to add a field in a legacy database you would have to bring the whole dataset offline, that is, make it inaccessible to users, modify it, change and recompile related programs, and so on. We'll talk more about that in the "Database Legacy" section of this chapter.

Another scalability aspect is that data typically lives longer than the hardware and software used to access and manipulate it, so it would not be very convenient to have to redesign the entire database to accommodate the current "flavor-of-the-month" development environment; for example, in case of a takeover or when company management suddenly decides to switch production environment from Java to C#.

User-friendliness

Databases are not just for programmers and technical personnel (some would say not for programmers — period). Nontechnical users constitute the majority of all database users nowadays. Accountants, managers, salespeople, doctors and nurses, librarians, scientists, technicians, customer service representatives — for all these and many more people, interaction with databases is an integral part of their work. That means data must be easy to manipulate. Of course, most users will access it through a graphical user interface with a predefined set of screens and limited functionality, but ad-hoc database queries and reports become more and more popular, especially among sophisticated, computer-literate users.