Interaction of -S and recursive-clients?

[Chris Thompson]

Our local university-wide recursive nameservers have

  options { /* ... */
   recursive-clients 5000;
   }

This is meant to be reached only at very bad times indeed. During a recent
network partition incident, I noticed that named logged

 named: general: error: socket: file descriptor exceeds limit (4096/4096)
 last message repeated 1194 times
 named: general: error: socket: file descriptor exceeds limit (4096/4096)
 last message repeated 780 times

a few seconds before it started on

 named: client: warning: client 131.111.***.***#*****: recursive-clients
   soft limit exceeded (4901/4900/5000), aborting oldest query

As far as I can see, the only way to increase the socket limit is to use
-S in the named argument list. Should one always set this (at least as)
high as the recursive-clients setting? (Actually, I am more tempted to
try decreasing recursive-clients from 5000 to 4000 as these numbers are
reached only when the network has gone pear-shaped anyway.)

-- 
Chris Thompson
Email: cet1 at cam.ac.uk