An installation's data and application programs must be protected from unauthorized access — both internally (employees) and externally (customers, business partners, or hackers). In working with z/OS®, you need to understand the importance of security and the z/OS facilities used to implement it.

Over time, it has become easier to create and access computerized information. No longer is system access limited to a handful of highly skilled programmers. Information can now be created and accessed by almost anyone who takes a little time to become familiar with the newer, easier-to-use, high-level inquiry languages.

More and more people are becoming increasingly dependent on computer systems and the information they store in these systems. As general computer literacy and the number of people using computers has increased, the need for data security has taken on a new measure of importance. No longer can the installation depend on keeping data secure simply because no one knows how to access the data.

Making data secure encompasses more than just making confidential information inaccessible to those who should not see it. It also includes preventing the inadvertent destruction of files by people who may not even know that they are improperly manipulating data. Good data security practices reduces the likelihood of unauthorized persons accessing, modifying, or destroying data, either inadvertently or deliberately.

Access, in a computer-based environment, means the ability to do something with a computer resource (for example, use, change, or view something). Access control is the method by which this ability is explicitly enabled or restricted. Computer-based access controls are called logical access controls. These are protection mechanisms that limit users' access to information to only what is appropriate for them.

Logical access controls are often built into the operating system, or may be part of the logic of application programs or major utilities, such as database management systems. They may also be implemented in add-on security packages that are installed into an operating system; such packages are available for a variety of systems, including PCs and mainframes. Additionally, logical access controls may be present in specialized components that regulate communications between computers and networks.