The Map Field to Multiple Columns dialog box enables you to map a field to more than one column when doing CMP mapping in the Sun Java System Application Server.
To map a field to more than one column:
Columns are from the tables you have mapped to this bean.
If you map a field to more than one column, all columns will be updated with the value of the first column listed. Therefore, if the value of one of the columns is changed outside of an EJB application, the value will only be read if the change was made to that first column. Writing a value to the database overwrites any conflicting changes made to any other columns.
You must also make sure that if you map more than one field to any of these columns, the mappings cannot partially overlap.
Consider the following three examples: