电子仓库目录下为什么会生成大量的unreferenced文件

An unreferenced file is a file that no longer has a valid association with any Windchill object. 
This can occur in the following scenarios:
All objects associated with the file have been deleted, leaving the file without any references.
A user removes the association to the file while updating the object.
Please refer to the following article for more information about unreferenced files and the procedure for cleaning them up.

https://www.ptc.com/en/support/article/CS383487?source=search