When you start an enterprise server, a utility called DFHZJCL2 runs automatically to check for some common set-up errors that might otherwise be hard to spot. For example, it checks that the system catalog and default allocation location are both usable. If a problem is found, it displays a message on the console log.
For example, should the catalog be unusable there will be a message in the log saying: "Catalog Open IVP test failed".
Once it has completed the validation DFHZJCL2 schedules the spool housekeeping by issuing a CICS START for transaction JCL1.