Internal
Enhanced Definition
In the mainframe and z/OS context, "internal" refers to components, processes, data, or resources that reside or are managed *within* the z/OS operating system environment or a specific program's execution scope, as opposed to external entities or interfaces. It denotes elements intrinsic to the system's operation or an application's local context, often implying direct system control or program-level encapsulation.
Key Characteristics
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- System-Managed: Often describes resources or services directly managed by the z/OS kernel or system control programs, such as memory allocation, task dispatching, or I/O supervision.
- Program-Scoped: Within an application, "internal" can describe data structures (e.g.,
WORKING-STORAGE) or subroutines (SECTIONs,PERFORMed paragraphs) that are defined and accessible only within that specific program or load module. - Directly Addressable: Internal memory (main storage) is directly addressable by the CPU, allowing for high-speed access, unlike external storage devices.
- Integrated Operations: Implies operations or components that are tightly integrated into the core functionality of z/OS or a subsystem (e.g., CICS internal transactions, DB2 internal routines).
- Not Externally Exposed: Typically refers to mechanisms or data that are not directly exposed to external systems or users, but are vital for the system's or application's internal workings.
Use Cases
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- Internal Program Logic: A COBOL program might use
PERFORMstatements to execute internal paragraphs orSECTIONs, keeping related logic encapsulated within the program's source. - Internal Data Structures: Defining record layouts in the
WORKING-STORAGE SECTIONof a COBOL program for temporary data manipulation, which are internal to that program's execution instance. - Internal System Buffers: z/OS and its subsystems (like CICS or DB2) utilize internal memory buffers for I/O operations, caching, and task management to optimize performance.
- Internal Subsystem Operations: CICS manages internal tasks and control blocks for transaction processing, largely hidden from the application programmer.
- Internal Storage Management: The z/OS Virtual Storage Manager (VSM) handles the allocation and deallocation of internal virtual storage for programs and
- Internal Program Logic: A COBOL program might use
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