This topic relates to the following sections:
Mapping the Fields of a Datasource
Maintain Tables and Fields Tab
Remove an unused field from Field Mappings
Should the situation arise where a field is set as part of the migration of data, but once mapping is being built that field is determined to not be relevant, the user may remove the field from the migration process. This change takes place within both the Field Mappings page and the Dataset Design Migrate page using the following steps:
Within the Migrate > Mappings, in the Field Mapping page, unlock the Mapping Details and set the field as Mapping Status = New and Build Status = New and save the changes.
Within the Catalog > Dataset Design page, click the Migration tab, select the field and click the Delete 
icon to remove this value from the
Migration process.
If this field is not mapped in any Releases where the dataset is used, then it is removed from the list for Migration, Tables and Fields, and Data Elements tabs of this dataset.
Remove an actively mapped field from Dataset Design
Actively mapped fields should not be removed from the associated Dataset Design. However, if one must be removed, the action will also delete the mapping and rules that are part of this rules conversion of data.
A warning message will display should an active, mapped field be set for deletion. The user may click OK to proceed or CANCEL to exit without making the change. The result will remove the field from Data Elements page and Migration page of Dataset Design.The field will be removed from the Target table and Target Source mappings, and any ETL Rules that include this field will update to remove it as well.
Add a Target Field to Field Mappings
There are situations where the user may want to add a field to the migration that was not included or was removed in the past. As example:
A field might be added to the target system, and now needs to become part of an existing migration of data.
A field may have been removed because it was not needed, and now is relevant for the migration.
Adding a field to the target table stored in a dataset requires working in the Datasource Tables, Dataset Design, and Mappings sections of the system. The steps are as follows:
First, the field must be added to the Target System Table if it does not exist there. Refer to section Catalog > Datasources > Dataset Design > Adding & Editing Datasources > Adding & Editing Tables or Columns for more details of this process.
Using pathway Catalog > Dataset Design, click to view the Tables and Fields tab. Click to Edit 
the Table and then click the Sync Field 
icon. This icon refreshes from the Datasource any fields that are not showing on the list on the Tables and Fields tab.
Note
The Migration and Data Elements tabs are not updated at this time.
Next, locate the added field and update for Data Element Active. This action is complete.
Once the field has been added to the Dataset, it is automatically added to the Target and Working tables. The field is added to mappings as well.