The lack of atomic commits in VSS, CVS and ClearCase caused absolutely horrific problems, even on small teams.
Re:Sunsetting Mercurial Support in Bitbucket
by silverbacknet on Tuesday August 20, 2019 @11:15PM
(#20754307)
I remember when you basically had to yell "Committing!" and "Done committing!" to the whole room. Woe be unto those companies that tried to use VSS or CVS with more than a roomful of developers.
They called it "multiple checkout", and the manual strongly recommended you do not turn it on.
The software had issues with corruption due to operations not being atomic.