The variables RES_RETRY and RES_TIMEOUT are useful on AIX systems for resolving name services problems.
Add them to the /etc/environment file and this may help to speed up the failover times to the next DNS server in the /etc/resolv.conf file if the first server is not responding.
These values mean that DNS requests (nslookup) will timeout after 1 second and then move on the the next DNS server in the list.
RES_RETRY=1
RES_TIMEOUT=1