With the exception of kernel patches (and even then, tools like ksplice exist), you generally do not have to restart the OS to apply patches. If the DB itself

With the exception of kernel patches (and even then, tools like ksplice exist), you generally do not have to restart the OS to apply patches. If the DB itself is being patched, then yes, you’ll restart the DB process, but it’s also not difficult to automate failover.