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