The first Sun was installed at a Starlink site in March 1990 and hence the total elapsed migration time has been 5 years. However, the majority of the hardware purchasing has taken place in the last 3 years. During this period, we have had to run VMS and Unix in parallel. The VAXes at a given site have then been switched off when virtually all of the software which is used at that site has been ported to Unix and when there is sufficient Unix hardware at that site to support the resident user community. Unfortunately, it has been necessary to divert funds from software effort in order to complete the move so swiftly.
Further details are available from the author.
One of the most vital aspects of the migration was the provision of migration aids for users. Unix utilities which come bundled with the operating system. This allowed users continued access to their old VMS files when they ventured onto the Unix machines. We used DEC's UCX product. Hence, we adopted the friendly pine system which has proven very popular, even with VMS diehards.