||I think I have some information to post that is relevant to this topic. It’s certainly true that you can get the “Can not add field to the selected table/feature class because it is in use by another application/user.” error message for both adding and deleting fields to a shapefile if ArcCatalog already has a lock on the shapefile, or if you have more than one map document open at the same time with the same shapefile open in each. The situation I encountered, however, appears to relate to the length of the path. I couldn’t find any information about this in the Help or in the forums here on the support site.
I often construct pretty long shapefile names because I use the names as a form of documentation for what I have done to derive the file. So, I have a series of files in one map document named as follows, with the year varying from file to file:
The length of the path for the files (including the file name) is 138 characters. I don’t know whether it makes a difference, but I am using relative paths in the map document. When I tried to delete a field from one of these files, I got the “Can not delete the selected field from the selected table/feature class because it is in use” error message. In trying to figure out why I got this message, I closed ArcCatalog and also did a cold boot of the computer (Windows XP Pro)--neither helped. The only variation that prevented the error message was to include only one of the files by itself in a map document. It began to seem as if ArcMap thought that the filenames were identical, even though the full, distinct name of each file appeared in the Source tab of its Properties box.
I started experimenting with renaming two identical shapefiles by placing a “1” and “2” in the file names in various positions to the left of the end of the filenames. When I inserted “1” and “2” in the following position (and positions to the right of this), ArcMap started treating the files as distinct, rather than as identical files:
Does this mean that there is a 128 character limit to the path for a shapefile?