FCQRDATA - Fast Communication Query Data

Enhanced Definition

FCQRDATA (Fast Communication Query Data) is an internal VTAM (Virtual Telecommunications Access Method) data area on z/OS designed to provide quick access to critical communication-related statistics and status information. Its primary purpose is to enable efficient, low-overhead monitoring and analysis of VTAM's network activity and performance.

Key Characteristics

- VTAM Internal Structure: It is a core internal control block or data area maintained directly by VTAM, reflecting its operational state.
- Performance-Oriented: Optimized for rapid retrieval of data, making it highly suitable for real-time or near real-time network monitoring tools.
- Communication Statistics: Contains a wealth of data related to active SNA sessions, buffer pool usage, I/O counts, error statistics, and other key performance indicators for VTAM-managed traffic.
- Programmatic Access: Typically accessed by authorized system monitoring products or custom programs through VTAM's internal programming interfaces (e.g., specific VTAM macros or direct control block mapping).
- Dynamic Updates: The data within FCQRDATA is continuously and dynamically updated by VTAM as network activity occurs, ensuring it reflects the most current state of the communication environment.

Use Cases

- Real-time Network Monitoring: Used by network performance monitors (e.g., IBM's Network Performance Monitor - NPM, or third-party tools) to display current VTAM session status, buffer utilization, and data transfer rates on dashboards.
- Troubleshooting Communication Issues: Helps system programmers and network administrators quickly diagnose problems such as slow response times, session drops, or excessive retransmissions by examining VTAM's internal state and error counters.
- Capacity Planning: Provides valuable historical data (when collected over time) that can be analyzed to understand network growth, identify peak usage patterns, and forecast resource requirements for future planning.
- Application Performance Analysis: Allows for the correlation of application response times with underlying VTAM network performance metrics to pinpoint communication-related bottlenecks affecting user experience.

Related Concepts

FCQRDATA is intrinsically linked to VTAM (Virtual Telecommunications Access Method), as it's a fundamental internal data structure maintained by VTAM to manage SNA (Systems Network Architecture) communications on z/OS. It complements SMF (System Management Facilities) records, which provide a more comprehensive, historical, and often delayed view of system activity, whereas FCQRDATA offers a more immediate, granular snapshot of VTAM's operational state. Monitoring tools like NPM (Network Performance Monitor) leverage FCQRDATA (among other sources) to present real-time network performance dashboards and alerts. While primarily SNA-focused, understanding FCQRDATA can indirectly aid in analyzing overall mainframe network health, even in environments increasingly dominated by TCP/IP, by providing insights into the remaining SNA footprint.

Best Practices:

Utilize Specialized Monitoring Tools: Leverage established network performance monitoring products that are specifically designed to efficiently extract and interpret FCQRDATA, rather than attempting to build custom, complex parsers.
Monitor Key Metrics Regularly: Identify critical VTAM metrics within FCQRDATA (e.g., buffer pool utilization, active session counts, error rates) and monitor them continuously to detect anomalies and potential issues early.
Correlate with Other Data Sources: Combine FCQRDATA insights with SMF data, application logs, and TCP/IP stack statistics for a holistic and comprehensive view of system and network performance.
Understand VTAM Control Block Structures: For advanced troubleshooting or custom development, a solid understanding of VTAM control block structures (e.g., using DSECTs in assembler) is crucial to correctly interpret the raw data.
Be Mindful of Overhead: While designed for fast query, excessive or inefficient polling of FCQRDATA by multiple tools can still introduce some system overhead;