Domino memory errors

I have been seeing the following errors in my server log 
(/var/log/notes/domino.log):


Dropped 5 sessions due to error creating task

and,

** Error attaching to shared memory 
[loc=AllocSharedRegion,errno=12,ptr=ffffffff] -- check OS kernel 
configuration and Notes_SHARED_DPOOLSIZE environment variable.


I have added NOTES_SHARED_DPOOLSIZE=4096000 to /etc/sysconfig/domino as 
per a NotesBench article, but I still receive these errors.  Is there 
something else that I'm missing?

Scott Blayney