Cannot increase open file descriptors above 1024

[Ibrahemoo Ghost]

I use FreeRADIUS Version 3.0.20 as both proxy and (auth/acct) server.
I have more than 80 realms with over 180 clients connected. Every one
of them is redirecting to a different site file with separate sql
module to a seperate database in the same db server.

My problem is with this large amount of databases and tables i hit the
fixed limit of 1024 open file descriptors and the radius.log file
shows:
mysql error: can't create unix socket (24)

I double checked with:
ls /proc/${freeradius_pid}/fd | wc -l
it prints 1024 that's why I am sure its problem with the open files limit

I tried to increase it manually but with no luck at all.
Whenever I increase it the freeradius server stops working.

So is there something I can do to increase the file descriptors limit ?
Or am I doing something wrong?