The Data Table window opens, displaying the feature data contained in your map. If you have to a layer in your map, the joined data is displayed, but it is gray. You cannot edit it in the Data Table. Instead, select the original data source and update that in the Data Table. Your changes will appear the next time you display this data as joined data.
When you edit data related to a feature, that feature is checked out automatically (and the Update Edits Automatically setting is turned on). Non-feature data cannot be checked out, so all edits to that type of data are written back to their underlying sources immediately. You cannot edit non-feature data unless you are connected to its source. See .
Some data fields are “constrained” to allow only certain values. When you enter values for constrained fields, you are prompted to enter only valid values. For example, the prompt might tell you to enter only values between one and ten.