Integrity Checking

Enhanced Definition

Integrity checking in the mainframe context refers to the process of verifying that data, system components, or application states are correct, consistent, and adhere to predefined rules and constraints. It ensures the reliability, accuracy, and trustworthiness of information and the operational stability of z/OS systems.

Key Characteristics

- Scope: Can apply to data within databases (e.g., DB2, IMS), files (e.g., VSAM, sequential datasets), system configurations, or application logic and state.
- Mechanisms: Implemented through database constraints (e.g., PRIMARY KEY, FOREIGN KEY, CHECK clauses in DB2), application-level validation logic (e.g., COBOL programs), system utilities (IDCAMS VERIFY, DB2 CHECK DATA), and specialized integrity checkers.
- Timing: Can be performed in real-time during data entry or updates, as part of batch processing, or periodically via scheduled maintenance jobs to proactively identify issues.
- Types: Encompasses referential integrity (relationships between tables), entity integrity (uniqueness of records), domain integrity (validity of data types/ranges), and structural integrity (physical consistency of data structures).
- Impact of Failure: Integrity violations can lead to incorrect reports, application errors, system abends, data corruption, and loss of business trust, necessitating robust recovery procedures.

Use Cases

- DB2 Referential Integrity: Defining FOREIGN KEY constraints in DB2 DDL to ensure that a value in a child table always references an existing PRIMARY KEY in a parent table, preventing orphaned records.
- COBOL Application Data Validation: A COBOL program validating input fields (e.g., numeric-only, date format, range checks) from a transaction before processing or updating a VSAM file or database.
- IMS Database Consistency Checks: Using IMS utilities like DFSDDLT0 or DBRC (Database Recovery Control) to verify the structural and logical consistency of IMS databases and their associated logs.
- VSAM File Integrity: Running the IDCAMS VERIFY command in JCL to ensure the structural integrity of a VSAM KSDS, especially after an abnormal termination, by rebuilding its index component.
- System Log Integrity: Verifying the consistency and completeness of system logs (SMF, SYSLOG) to ensure reliable audit trails and system event records for compliance and troubleshooting.

Related Concepts

Integrity checking is fundamental to Data Reliability and Data Consistency within the z/OS environment. It is a core component of Database Management Systems like DB2 and IMS, where ACID properties (Atomicity, Consistency, Isolation, Durability) are enforced, with consistency heavily relying on robust integrity mechanisms. It is closely linked to Application Development, as robust COBOL and PL/I programs must incorporate validation logic. Furthermore, it underpins Backup and Recovery strategies, as restored data must also pass integrity checks to be considered valid.

Best Practices:

Leverage Database Constraints: Define PRIMARY KEY, FOREIGN KEY, CHECK constraints, and NOT NULL attributes directly within DB2 DDL to enforce data integrity at the database level, reducing application code complexity.
Implement Robust Application Validation: Incorporate comprehensive input validation and business rule checks within COBOL or PL/I application logic to prevent invalid data from entering the system, complementing database-level checks.
Regular Integrity Utilities: Schedule periodic execution of database utilities (e.g., DB2 CHECK DATA, IMS DFSDDLT0, IDCAMS VERIFY) to proactively identify and correct potential integrity issues before they escalate.
Audit and Log Violations: Implement mechanisms to log and alert on any integrity violations detected, providing an audit trail for investigation, correction, and compliance reporting.
Design for Error Handling: Develop applications with robust error handling routines to gracefully manage and report integrity failures, preventing data corruption and system abends, and facilitating quick recovery.