Oracle\'s instructions specify setting LD_LIBRARY_PATH. This makes my application dependent on random users\' configuration and is very troublesome to set up.
For anyone playing with Solaris (like me!) coming from a Linux background, I found that @David Phillips solution worked well using the Solaris command crle -u -l /opt/instantclient
Thanks to post http://chrismiles.info/systemsadmin/solaris/articles/ld-path-customisation-on-solaris/