Don't know NSIS has "transaction" function

When installing file, there will be something happend such as file locked, so we can copy files over and we can't stop the service, if installer fails, then need to rollback all the files which has copied? Just like windows Installer does. NSIS has this function now??????
want to know.

Actually you could use the integrated callbacks such as .onUserAbort, .onInstFailed, and .onInstSuccess to perform a rollback/cleanup.