Each SQL call that is issued by a CICS® VT DDM has a predicate. The predicate columns are the DB2® primary key columns for regular call or the alternate index columns if you are using an alternate index path. Your FBE may have to take this into consideration.
Your FBE uses EXFUNCT to decide if it is building a VSAM field value or a DB2 column value. If your FBE operates on a single field, the exit code is the same for a key and non-key field. An example is DATEFBE which is explained in Reformatting a date field.
More complex FBEs on a key or an AIX® field may have to use the fields EXVSABLD and EXDB2BLD in conjunction with EXFUNCT. An example of a more complex FBE is CTLRECF, which is explained in FBE for managing a control record.
To illustrate this, consider the case where an application program issues a direct call, such as a START BROWSE, and the key field is managed by an FBE. When the call is processed in CICS VT, the exit is executed at multiple points in the call.
Your exit must taken account of the values of EXFUNCT, EXVSABLD, and EXDB2BLD to drive the appropriate logic.