Environment Variable

Enhanced Definition

In the z/OS environment, an environment variable is a dynamic named value that can affect the way running processes behave. Primarily utilized within the `OMVS` (UNIX System Services) component, it provides configuration information to programs, scripts, and the shell, influencing their execution context and resource access. An environment variable in the z/OS context is a named value that provides configuration information to programs, primarily within the z/OS UNIX System Services (USS) environment, and for applications written in languages like Java, C, or C++. It allows programs to modify their behavior or access system-specific settings without requiring recompilation.

Key Characteristics

- Scope: Environment variables are typically local to a process and inherited by any child processes it creates, allowing for hierarchical configuration.
- Usage Context: Most prevalent in OMVS (UNIX System Services) for C/C++, Java, Perl, Python, and shell scripts, providing a UNIX-like configuration mechanism.
- Setting Methods: Can be set interactively in a shell using export VAR=value, within shell scripts, via BPXPRMxx PARMLIB member for system-wide defaults, or programmatically within applications.
- Persistence: Not inherently persistent across system reboots or new shell sessions unless explicitly set in system-wide configuration files (like BPXPRMxx) or user profile scripts (.profile).
- Access: Programs access their values through standard APIs like getenv() in C, System.getenv() in Java, or the VALUE() function in REXX when running in OMVS.
- Case Sensitivity: In OMVS, environment variable names are generally case-sensitive, adhering to UNIX conventions.

Use Cases

- Specifying Library Paths: Setting LIBPATH for dynamically loaded libraries or CLASSPATH for Java applications to locate required .jar files and classes.
- Application Configuration: Providing runtime parameters to applications, such as MQSERVER for IBM MQ client connections or database connection strings.
- Controlling USS Behavior: Influencing OMVS system behavior, for example, _BPX_SHAREAS to control address space sharing for fork()/exec() operations.
- Locale and Character Set: Defining the language and character encoding for OMVS processes using variables like