Explained: CICS Error Handling

A CICS transaction reads a customer record. The record does not exist. The program does not check the response code. It continues with uninitialised Working Storage, writes garbage to a VSAM file, and returns a confirmation to the screen. The customer's record is now corrupt. Nobody knows yet. Error handling in CICS is not optional. Every CICS command can fail. Files return `NOTFND`. DB2 returns lock timeouts. Programs abend with `ASRA`. The … Read More

Explained: CICS Link Modules

A CICS transaction arrives. It validates the input, applies some business rules, looks up a customer record, and calculates a result. If all of that logic lived in one monolithic COBOL program, changing the business rules would mean recompiling and redeploying the entire thing. Testing the calculation in isolation would be impossible. Sharing the customer lookup with ten other transactions would mean copying the code ten times. This is why CICS p… Read More