In some circumstances it is useful to be able to distinguish between table entries that are live, and inactive table entries that are present only because they belong to historical data. The inactive table entries need to be present so that historical data is displayed correctly, but they shouldn't be used when creating new data.
To flag a table entry as inactive, create a one character field field to hold the inactive indicator and then choose that field in the Inactive Table Entry indicator drop down list.
This property is in the Code Table Definition tab.