On Tue Feb 13 19:39:22 2018, mkrishna@palcnetworks.com wrote:
> I am able to see exact 999 file descriptors as pasted below.
> I have got this output using '*lsof*'.

=> you have reached the silly (but not real) limit of 1000 open
file descriptors of Linux. As it often hurts with named there are
a lot of documentation about to break this limit.

Unfortunately it is a bit late here but as it is a recurrent issue
someone in another timezone should be able to help you.

BTW very recent versions of ISC DHCP can be compiled with
a better replacement for select() which can show performance
issue with a large number of descriptors.