In short, the answer is, "No".
In SunOS 4.X, it was a requirement that you needed "at least" as much swap
space as physical memory, because the OS would map all physical memory to
swap. In Solaris 2.X, it no longer does that, and the swap space is used
only when you don't have enough RAM. Therefore, if you have enough RAM,
the swap space may never be used.
Therefore, many people suggested that monitoring the system to see how much
virtual memory is being used up and then determine if swap space is necessary.
Another good idea was to write a program that monitors the usage and adds
swap space when virtual memory is low (using mkfile and swap commands).
The one issue that I'm yet sure about is, whether or not a disk swap space
is required to get a crash dump, or if creating a crash directory is