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Height

Vertical Size

Enhanced Definition

In the context of IBM mainframe systems, "height" primarily refers to the vertical dimension of a display screen, such as a 3270 terminal, or the number of lines on a printed page. It defines the maximum number of lines of text or data that can be presented vertically within a given display or print area.

Key Characteristics

- Fixed Dimensions: For 3270 terminals, common screen heights are fixed, often standardized to 24, 32, 43, or 27 lines, typically paired with a specific width (e.g., 24x80, 43x80, 27x132).
- Application-Controlled: Applications running on z/OS (e.g., CICS, TSO/ISPF) often adapt their screen layouts and data presentation based on the detected terminal height.
- Printer Page Length: For batch reports, "height" corresponds to the number of lines per page, controlled by JCL parameters like LINES on the OUTPUT statement or within print utilities.
- Programmatic Access: Programs can query terminal characteristics, including height, using specific APIs (e.g., TSO/ISPF services, CICS terminal control) to tailor output.

Use Cases

- 3270 Terminal Emulation: Configuring a 3270 emulator to match a specific screen height (e.g., 24 lines) to ensure proper display of legacy applications and prevent truncation.
- ISPF Panel Design: Developers design ISPF panels considering different screen heights to ensure all fields are visible or to provide scrolling mechanisms for larger panels.
- Batch Report Formatting: Specifying the number of lines per page for a batch report using JCL to fit standard paper sizes or user preferences for readability.
- CICS Screen Mapping: Using BMS (Basic Mapping Support) to define map sets that can dynamically adjust to different terminal heights, often by defining multiple map sizes within a single map set.

Related Concepts

Height is closely related to screen resolution or terminal dimensions, which define the overall display area. It directly influences ISPF panel design, BMS map sets in CICS, and JCL SYSOUT parameters for print output. Understanding screen height is crucial for designing user interfaces that are both functional and aesthetically pleasing on 3270 terminals, ensuring data is presented without truncation or excessive scrolling.

Best Practices:

Design for Smallest Common Denominator: When developing 3270 applications, design for the smallest common screen height (e.g., 24 lines) to ensure compatibility across all user environments.
Utilize Scrolling: For applications requiring more vertical space than the standard screen height, implement scrolling mechanisms (e.g., ISPF SCROLL command, CICS paging) rather than assuming larger screen heights.
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