When you map a VSAM file, you define the association between the record in its VSAM and DB2® forms.
In Figure 1, each field is mapped to one column in DB2. To process a GET-type VSAM call, CICS® VT performs the following steps:
If you have mapped an FBE on a field, it is responsible for building the field values and performing any data transformation. It must do this for GET-type calls and PUT/WRITE/REWRITE calls. An example of how to map an FBE is shown in Mapping an FBE. You can map multiple FBEs in the same file, and you can use a single FBE to build several fields or columns. When an FBE ends, CICS VT builds the remaining fields in the record.
An IRD operates at record-level, and is only invoked for PUT/WRITE/REWRITE calls. You can only have one IRD for any DIM.
An IRD is always processed after the entire DB2 record is built. If you have FBEs and an IRD on the same file, the FBEs will always have executed before the IRD. When you map an IRD, you specify the specific point in the VSAM call that the exit is invoked. The options are as follows:
A parameter is passed to the IRD to indicate the point at which it is being invoked.
An example of mapping an IRD is shown in Mapping an IRD.