(excerpt from
http://www.hp-partners.com/ptc_publi.../2x_swap2.htm)

To add a raw swap partition to a Solaris 2.x system, identify an unused partition on a disk. Traditionally, slice 1 is used for swap space. Add the following entry to /etc/vfstab, taking care to use the correct device name:

/dev/dsk/c0t1d0s1 - - swap - no -

Enable the new partition with the swap command:
swap -a /dev/dsk/c0t1d0s1

Check your change:

swap -l

swapfile dev swaplo blocks free

/dev/dsk/c0t3d0s1 32,25 8 164040 164040
/dev/dsk/c0t1d0s1 32,9 8 164040 164040