DEFAULT MODIFIES

The DEFAULT MODIFIES option controls what Span Accessory writes to its updates files for all data sets except those for which you override DEFAULT MODIFIES, as explained in the next section.

The DEFAULT MODIFIES options are as follows:

DEFAULT MODIFIES AFTER IMAGES ONLY

%DEFAULT MODIFIES BEFORE AND AFTER IMAGES

Use only one of these two options at a time. If both are uncommented, the last one in the list takes precedence.

You can override this value for individual data sets. See Individual Data Set Options.

Selecting DEFAULT MODIFIES

Span Accessory can write the modified record only (AFTER IMAGE), or it can write the record as it looked before the modification (BEFORE IMAGE) and how it looked after the modification (AFTER IMAGE).

Typically, your decision on whether or not to save AFTER IMAGES ONLY or save BEFORE AND AFTER IMAGES is based on what you will do with the output file. Use the following table as a guide for which DEFAULT MODIFIES option to select.

DEFAULT MODIFIES

Description

AFTER IMAGES ONLY

Span Accessory writes only the resulting change to the Span Accessory output file. In other words, Span Accessory writes the record the way it looks after the update. Selecting AFTER IMAGES ONLY is useful if your database has keys that are unique and that won’t change (for example, a customer number). This way, a client database can always find records via the key and therefore process any changed records.

BEFORE AND AFTER IMAGES

In this case, Span Accessory writes both the before image and the after image to the Span Accessory output file. This is the same as converting any modification of an existing record to a DELETE/CREATE pair (DELETE contains the before image; CREATE contains the after image).

Selecting BEFORE AND AFTER IMAGES is useful when the DMSII database allows key fields to be updated. It ensures that even if the key of a record is changed, the client database can process the change correctly. For example, when the output file contains before and after images, the client software can search for the before image and find a match before it makes the update.

The disadvantage of selecting BEFORE AND AFTER IMAGES is that the number of records for modifies doubles and could result in additional disk space requirements in the output files and additional processing time to write and read the records.