Fan-In
Enhanced Definition
In mainframe computing, "fan-in" refers to the number of other modules, programs, or components that directly call, invoke, or depend on a single specific module, program, or resource. A high fan-in indicates that a particular component is heavily utilized and critical across various parts of an application or system.
Key Characteristics
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- Dependency Measurement: Quantifies the inbound dependencies, showing how many upstream components rely on a specific downstream component (e.g., a
COBOLsubroutine, aDB2stored procedure, aCICSprogram). - Criticality Indicator: Components with high fan-in are often core services, utility routines, or shared data structures, making them critical to overall system functionality and stability.
- Impact on Change Management: Modifications to a high fan-in component can have widespread ripple effects, necessitating extensive impact analysis and regression testing across numerous calling programs or jobs.
- Potential Performance Bottleneck: If a high fan-in
- Dependency Measurement: Quantifies the inbound dependencies, showing how many upstream components rely on a specific downstream component (e.g., a