COBOL File Handling Basics: Sequential Files, File Status, and Practical Flow
Learn how COBOL file handling works with SELECT, FD, OPEN, READ, WRITE, CLOSE, and file status checks.
Mainframe Articles
Practical tutorials for mainframe learners and working developers.
JCL JOB, EXEC, and DD Statements Explained for Beginners
Understand the three core JCL statements used in almost every mainframe batch job: JOB, EXEC, and DD.
JCL Return Codes and Conditional Execution: How Batch Flow is Controlled
Learn how JCL return codes control step execution using COND, IF/THEN/ELSE, and production-safe patterns.
GDG Basics in JCL: Generation Data Groups Explained with Examples
Understand GDG datasets, relative generations, and common JCL usage patterns for daily batch processing.
DB2 Cursor Basics for COBOL Programs
Learn how DB2 cursors work in COBOL programs and when to use DECLARE, OPEN, FETCH, and CLOSE.
DB2 Indexes and Access Paths Explained Simply
Understand how DB2 indexes influence access paths and why EXPLAIN matters for performance tuning.
CICS Transaction Flow for Beginners
Learn how a CICS transaction moves from terminal input to program execution and response display.
COMMAREA Explained with a Practical CICS Example
Understand how COMMAREA passes data between CICS programs and pseudo-conversational transactions.
VSAM KSDS Explained: Keys, Records, and IDCAMS Basics
Learn what a VSAM KSDS is, why it is used, and how mainframe programs access keyed records.
Common Mainframe Abends Every Beginner Should Know
Learn common mainframe abends such as S0C7, S0C4, SB37, and how to approach production troubleshooting.
How AI Can Help Mainframe Documentation Without Risking Production Quality
Practical ways to use AI for mainframe documentation, test cases, summaries, and modernization support with guardrails.