All service startups in unix are handled by /sbin/rc? scripts. Just replace the ? by the runlevel. In this case, since it will be applications and databases that will be starting up, the startup script is /sbin/rc3. The /sbin/rc3 script in turn calls different scripts in the /sbin/rc3.d directory. You can write the startup scripts for the dbase/app and put it in the /sbin/rc3.d directory.

If you are new to the unix world, you might want to read up on how the HP-UX system boots.