Can anyone see any potential harm with changing a field type from short text to long text? I have a inherited db that has a field designated as short text. At design time, discussion decided that there would never be a need for more than 255 chars. I guess the saying never say never is true. Now they need more characters. There is no index on the field.
@TomKosel In general, no, there should be no problems with storing additional data.
That said, there are some differences in the way Long Text and Short Text datatypes can behave, so you do need to be aware of things that might be different. Two that come to mind are Text Format and Append Only. Both supported in Long Text. You can insert either Plain Text or Rich Text in a Long Text field (Support for fonts and colors, etc.) You can designate how new text is added. Since these are NOT properties you'd have used with Short Text, though, it should not be an issue.