I just learned about an Oracle builtin package called DBMS_JOB, that lets you schedule PL/SQL programs for periodic execution, somewhat like cron, although certainly not as simple (and when something's not as simple as cron, you're really in bad shape!). This may be something everybody knows about, but it's brand new to me. I've been looking for the answer to "How do things happen automatically in the database without user intervention or help from operating system services?" for awhile now.
