IGD

DFSMS Prefix

Enhanced Definition

`IGD` is a standard three-character prefix used by IBM z/OS to identify modules, macros, and messages associated with the Data Facility Storage Management Subsystem (DFSMS). It serves as a consistent identifier for components that manage storage, data sets, and volumes within the z/OS environment.

Key Characteristics

- System-Wide Identification: Consistently used across all DFSMS components, including SMS (Storage Management Subsystem), DFSMShsm, DFSMSdss, DFSMSrmm, and OAM.
- Message Prefix: Appears at the beginning of messages issued by DFSMS components, such as IGD001I (informational), IGD17101I (SMS allocation message), or IGD306I (DFSMS initialization message).
- Module and Macro Naming: Used as a prefix for load module names (e.g., IGDVSM00 for SMS Volume Selection Module) and system macros related to DFSMS functions.
- Documentation Reference: Helps users and system programmers quickly identify relevant sections in IBM documentation when troubleshooting or researching DFSMS-related topics.
- Error and Status Indication: IGD messages often provide critical information regarding storage allocation, data set migration, backup, recall, and overall storage subsystem health.

Use Cases

- Troubleshooting Storage Allocation: When a job fails with a storage-related error, IGD messages in the job log (e.g., IGD17290I for space not available) help diagnose the specific issue.
- Monitoring DFSMS Health: System operators monitor SYSLOG for IGD messages to track the status of DFSMS components, identify potential issues like full volumes or failed migrations, and ensure storage availability.
- Automating System Responses: Automation tools can be configured to intercept specific IGD messages (e.g., IGD306I indicating SMS initialization) and trigger automated actions or alerts.
- System Programming and Customization: When developing exits or customizing DFSMS behavior, system programmers often interact with IGD-prefixed macros or modules.
- Auditing and Reporting: Analyzing IGD messages can provide insights into storage usage patterns, allocation failures, and the effectiveness of storage management policies.

Related Concepts

IGD is intrinsically linked to DFSMS itself, as it's the identifier for all its sub-components. It frequently appears in conjunction with SMS (Storage Management Subsystem), providing messages related to storage class, data class, management class, and storage group processing. IGD messages are often found in JCL job logs, indicating issues with DD statement parameters or storage requirements. These messages are written to the SYSLOG and can be viewed via tools like SDSF, making them crucial for system monitoring and problem determination.

Best Practices:

Monitor IGD Messages: Regularly review SYSLOG and job logs for IGD messages, especially those indicating errors, warnings, or critical system events, to proactively address storage issues.
Consult IBM Documentation: When encountering an unfamiliar IGD message, always refer to the z/OS MVS System Messages manual for a detailed explanation, system programmer response, and problem determination steps.
Implement Automation: Configure automation routines to respond to common IGD messages, such as those indicating out-of-space conditions, to prevent job failures or system outages.
Understand SMS Constructs: A thorough understanding of SMS policies (data class, storage class, management class, storage group) is essential for interpreting IGD allocation messages and fine-tuning storage management.
Utilize Health Checker: Leverage z/OS Health Checker for DFSMS -related checks, which often report on conditions that would otherwise manifest as IGD messages, providing early warning of potential problems.