Not sure about Solaris 5.10, but Linux (at least on Redhat) these days only shows you the memory segments if the process has read access. So unless you are root or the process running the Sybase server, you won't see the shared memory segments reported by ipcs -ma
Can you see the shared memory segments with the user running the Sybase ASE process?
Maybe something similar implemented on Solaris (maybe RBAC specific?)
Better to ask this on a Solaris forum...