How to increase file descriptors max limit on Linux

Today my DBA reported that the server she was working on was spitting out “too many open files” errors and no new processes could be started.
This is a common problem with DB servers with heavy transactions. In my environment there are 6 DB instances running on the server. No quite the optimized setup I would say.
The fix was to increase the total file descriptors kernel parameter count in the /etc/sysctl.conf file. I doubled my limit from 8192 to 16384.
The walk through,
1. Find out what the current open file descriptor limit is.

~# more /proc/sys/fs/file-max

~# 8192

or

~# sysctl -a | grep fs.file-max

~# fs.file-max = 8192

2. View how many open file descriptors are currently being used.

~# more /proc/sys/fs/file-nr

~# 8191

3. View how many files are open. The number returned might defer as 1 file descriptor can have multiple open files attached to it.

~# lsof | wc -l

~# 10325

4. Edit the kernel paramneter file /etc/sysctl.conf and add line “fs.file-max=[new value]” to it.

~# vi /etc/sysctl.conf

fs.file-max = 331287

5. Apply the changes.

~# sysctl -p
~# fs.file-max = 331287

Problem fixed.