I am trying to use the Append tool with two .csv files. When I clik Run I get an error saying the target file is read-only. I have checked the permissions and is not read-only. I made sure no other programs were using the file as well. I even tried a reboot. Any suggestions would be appreciated.
Convert the csv files to a table/featureclass first, then append would be the first thing to try
I had the same issue when trying to append two shapefiles. One of my shapefiles had a joined table. Removing the join resolved my issue.
You would have to re-establish the join afterwards. It is still best with current versions of the software to use featureclasses rather than shapefiles. If you need to have one in the end, export after the append