Explained: CICS Storage Management

It starts as a performance problem. Response times climb. Tasks start queuing. Then a message appears on the operator console: DFHSM0133 CICS is under stress (short on storage above 16MB) . New transactions are refused. The region grinds to a halt and has to be recycled. Short on storage is one of the most disruptive CICS failures in production, and unlike most failures it builds gradually. A storage leak in one transaction, a DSA limit set too co… Read More

Architecture: VSAM

Every time a CICS transaction reads an account record, there is a file somewhere holding that record. It is not a relational table. It is not a flat file. It is a VSAM dataset: a structured, indexed file that CICS reads in under 10 milliseconds, keyed precisely on the account number, without scanning from the beginning. VSAM is the file system that mainframe application programs live on. Every CICS file definition points to a VSAM dataset. Every … Read More

Explained - Distributed Storage Systems

The blog post explores distributed storage systems, discussing their architecture, benefits, and key technologies like consistency models and replication. It covers use cases, scalability, fault tolerance, and the evolution of storage solutions for modern applications. Read More