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Interim/Temporary

Enhanced Definition

In the mainframe context, "interim" or "temporary" refers to resources, data, or processes that are short-lived, transient, or designed for a limited duration. These elements are typically created for immediate use, intermediate processing, or as a stopgap, and are not intended for long-term persistence or permanent integration into the system.

Key Characteristics

- Short Lifespan: Temporary resources are typically deleted, deallocated, or discarded automatically or manually after a specific job, task, session, or predefined period.
- Non-Persistent: Data stored in temporary datasets or memory areas is not intended for long-term archival or recovery; its loss after its intended use is expected.
- Dynamic Allocation: Often allocated dynamically by the operating system (z/OS) or application programs as needed, and released promptly upon completion.
- Resource Management: Requires careful management to prevent resource leaks, exhaustion (e.g., disk space, memory), or interference with other system processes.
- Performance Optimization: May be optimized for speed and efficiency over recoverability, given their transient nature and specific purpose.

Use Cases

- JCL Temporary Datasets: Using DD DSN=&&TEMPDSN in JCL to create datasets that exist only for the duration of a job, primarily for passing data between job steps.
- Program Work Areas: COBOL programs utilize WORKING-STORAGE sections for temporary variables and intermediate calculation results, or dynamically allocated memory for scratchpad data.
- Spool Files (SYSOUT): Output from batch jobs directed to SYSOUT queues is temporary until it is printed, viewed, or purged by the system or user.
- Testing and Development: Ad-hoc datasets, program versions, or configuration changes used for quick tests, debugging, or proof-of-concept work.
- System Dumps and Traces: Temporary storage of system state (e.g., SVC dumps, stand-alone dumps) or trace data for problem diagnosis, which is typically analyzed and then discarded.

Related Concepts

The concept of interim/temporary is fundamental to JCL (Job Control Language), where temporary datasets (&&DSN) are a core mechanism for inter-step communication within a batch job. It relates to memory management in z/OS, as programs frequently acquire and release temporary storage (e.g., GETMAIN, FREEMAIN) from system areas like the CSA, SQA, or private region. VSAM can also use temporary datasets for sorting or intermediate processing. Furthermore, it's tied to job scheduling and resource allocation, as temporary resources are managed within the lifecycle of a specific job or task, ensuring efficient use of system resources.

Best Practices:

Explicit Deletion/Disposition: Always ensure temporary datasets are explicitly deleted or managed by the system using appropriate DISP parameters (e.g., DISP=(NEW,DELETE) or DISP=(MOD,DELETE)) to prevent orphaned files.
Resource Limits: Define appropriate space, time, and record limits for temporary datasets and memory allocations to prevent system exhaustion or runaway processes.
Naming Conventions: Use clear and consistent naming conventions (e.g., && prefix for JCL temp datasets) to distinguish temporary resources from permanent ones, aiding in system management and debugging.
Security Considerations: Be mindful of sensitive data processed in temporary files; ensure proper cleanup and access controls are in place, even for transient data.
Performance Optimization: For high-volume temporary data, consider using in-memory tables, TEMPORARY VSAM datasets, or HIPERSPACE where appropriate to minimize I/O and improve performance.