I’ve been doing installs of Solaris 10 and then needing to set them up with SNMP. The first thing I noticed is that the system is running snmpd and not snmpdx. There is still an init.d file for snmpdx, init.snmpdx, and configuration files, so at first this confused me. After looking around the web, I found that Solaris 10 is moving to using snmpd (Net-SNMP) instead of the solstice version.
Finding that information out, I was able to determine that the configuration files for snmpd are located in /etc/sma/snmp/. To setup snmpd information, just modify the snmpd.conf and everything will work.
You can start and stop it form /etc/init.d/init.sma and it is started from /etc/rc3.d/S82initsma.