Q: Shapefiles - why do I have issues trying to do transactions against shapefiles?

There are several issues that one can encounter when trying to do transactions against shapefiles. On windows NTFS sometimes locks the files, and if many users are operating against a featureType backed by shapefiles, there can be corruption issues. If one is to read the first lines of the Shapefile DataStore docs, one would find that we don't actually recommend using Shapefiles to do transactions against, since they were designed as a file transfer format, not as a transactional database backend. We provide transaction support for users to experiment with how a WFS-T works, but for any real production instance, we highly recommend using a real spatial database, such as PostGIS, DB2, Oracle Spatial, or ArcSDE. MySQL also has growing spatial support, but the spatial stuff is in the non-transactionally secure tables, so we don't yet recommend it for high user production environments.