I could be wrong here so others can correct my errors as required. My take of that comment is COBOL is very popular on mainframe systems and those mainframe sy

I could be wrong here so others can correct my errors as required. My take of that comment is COBOL is very popular on mainframe systems and those mainframe system work around the concept of transactional batch processing. Processing is done in batches and the batches are control bay a transaction manager (i.e. CICS for example). In that model a COBOL program is just a step in the processing and is fully controlled the transaction manager. So in that sense it does just read and write data as one step in a much bigger batch of steps. As such the security is handled by the transaction manager layer.