What causes a feature dataset to suddenly become unversioned? I was editing a versioned feature class adding attachments. I needed to make an edit to an individual feature and I kept getting an error message that said I couldnt change a table without being in an edit session. Turns out that the dataset lost its versioning and I had to reregister as versioned. Is there something causing this to happen? I also discovered that multiple other datasets in the same SDE geodatabase also had to be registered as versioned again. I also ran MXD Doctor just to see if the MXD was causing an issue. As of now, everything appears to be working again but I want to know why this happened in the first place.