Serena Dimensions CM to RTC - Migration Tool
2 answers
I am not aware of any direct Dimensions->RTC migration tool provided by IBM.
There is a Subversion->RTC migration tool, so if you can find a Dimensions->Subversion migration tool, you could do it in two steps (Dimensions->Subversion, Subversion->RTC).
Or you can script it using the RTC command line (create an RTC sandbox on a stream with the components you want to import into, and then for each baseline in Dimensions you want to bring over into RTC, delete any files/folders under the component roots in that sandbox, extract that baseline from Dimensions into the RTC sandbox, checkin the sandbox changes into RTC).