When you run a mapping with a transformation that specifies a dictionary, the transformation compares the input field data to the data in the dictionary. If the transformation finds a match between an input value and a dictionary value, the transformation performs an action that the asset in the transformation defines. For example, the transformation might return the value in the valid column that corresponds to the input value.
Valid column behavior
The transformation searches every column in the dictionary except the valid column that the asset specifies. If you want the search operation to include the valid column data, add a copy of the valid column to the dictionary. By default, the valid column is the first or left-most column in a dictionary. You can create a dictionary that contains two identical columns of data.
Note: A test that you run in an asset in Data Quality reads a dictionary in the same way as a transformation reads a dictionary.
You can select any column with values that suit your data objectives as the valid column. You might specify different columns as valid in different rule statements. The contents of the dictionary columns determine if the dictionary can support different valid columns in different business cases.
You can design a useful dictionary with multiple occurrences of a single value in the valid column. For example, you might design a dictionary that identifies a list of cities by time zone. Avoid designing a dictionary with multiple occurrences of a single value in non-valid columns.
Dictionary download considerations
The Secure Agent can download a dictionary that an asset specifies when you test the asset or run a mapping or profile that reads the asset.
The Secure Agent uses the following guidelines to download dictionary data:
•When you test a step in a cleanse asset that reads a dictionary, the Secure Agent downloads every dictionary that the cleanse asset specifies.
When you test any other Data Quality asset, the Secure Agent downloads any dictionary that the test logic requires. If the asset specifies a dictionary that is not required during the test, the Secure Agent does not download the dictionary.
•When you run a profile or a mapping than references an asset that reads a dictionary, the Secure Agent downloads every dictionary that the asset specifies.
The Secure Agent downloads dictionaries to a directory on its host machine. You may decide to periodically check the download directory, for example to review the amount of disk space that the directory uses. For more information about dictionary downloads, see Verifying the dictionary download location.