1. remove /kernel/drv/vxdmp
2. relink DMP and RDMP directories
   

   • cd /dev/vx
   • mv dmp dmp.old
   • ln -s /dev/dsk dmp
      
   • mv rdmp rdmp.old
   • ln -s /dev/rdsk rdmp

3. (Solaris7/8 in 64 bit mode, rm /kernel/drv/sparcv9/vxdmp)
4. reboot

See also: Sun Bugid 4106644

To check if DMP is running type this:
$ modinfo | grep vxdmp