Immediate

Enhanced Definition

In mainframe computing, "immediate" refers to operations or data that are processed or accessed directly and synchronously, often without intermediate steps like memory lookups or job queueing. This concept applies to both data embedded directly within an instruction (immediate operand) and commands executed interactively and synchronously (immediate commands).

Key Characteristics

- Direct Execution/Access: Operations or data are handled without deferred processing or indirect addressing, providing instant results or data availability.
- Synchronous Nature: Commands execute and return control directly to the user or calling program, rather than submitting a batch job or queuing a transaction.
- Performance Optimization: For immediate operands in assembly, it eliminates a memory access cycle, potentially improving instruction execution speed. For immediate commands, it provides quick, interactive feedback.
- Limited Scope/Size: Immediate operands typically hold small, fixed-size values (e.g., 8-bit or 16-bit constants). Immediate commands are generally for quick, focused actions rather than complex workflows.
- Context-Dependent Syntax: The specific syntax and behavior of "immediate" elements vary significantly between contexts, such as assembly language instructions versus TSO/ISPF commands.

Use Cases

- Assembly Language Programming: Using instructions like MVI (Move Immediate) or CLI (Compare Logical Immediate) to load small constant values into memory locations or compare a register's content directly against a constant embedded in the instruction.
- TSO/ISPF Commands: Executing system commands directly from the TSO READY prompt or ISPF command line for quick queries, dataset allocations, or utility invocations (e.g., ALLOC FI(DD1) DA('MY.DATASET') SHR).
- CICS Transaction Processing: Certain CICS transactions or commands might be designed for immediate processing, meaning they are executed as soon as resources are available, rather than being queued for later execution or requiring a separate task initiation.
- Debugging and System Monitoring: Using immediate commands in TSO/ISPF or CICS to quickly check system status, display storage, alter settings, or issue operator commands during interactive debugging sessions or system administration.

Related Concepts

The concept of "immediate" is fundamental to understanding assembly language instruction formats, contrasting with register or storage operands that require additional lookups. In TSO/ISPF, immediate commands are a core part of the interactive processing environment, distinct from batch jobs submitted via JCL which run asynchronously. In CICS, it relates to transaction scheduling and resource management, differentiating from queued or deferred processing.