UltiSnips - The ultimate snippet solution for Vim. Send pull requests to SirVer/ultisnips!
@manishrjain UltiSnips uses the
filetype setting to filter snippets. If you open a .dat file, does :set filetype return dat?
If that is the case, than it is likely that UltiSnips ftdetect script is not sourced. The most likely source for that is a wrongly installed plugin manager
see SirVer/ultisnips#243 or https://github.com/SirVer/ultisnips/issues/264#issuecomment-40446248. There are other bugs with the same issue.