custom man page creation is not working and not indexed in Red Hat Enterprise Linux?

Issue

How do I make man see my custom man page.
I created a custom man page but the man command fails to display it unless the path to the man page is given explicitly.
This is what I did.

$ vi sys_raid.1 
# cp sys_raid.1 /usr/local/share/man8/
# gzip /usr/local/share/man/man8/sys_raid.1

But man will not find the page.

-bash-4.1$ man sys_raid
No manual entry for sys_raid

The MANPATH var comes out empty because according to its own man page, it will show empty when reading the default paths from /etc/man.config.

-bash-4.1$ echo $MANPATH
[...no output...]

This works on my working directory.

$ man ./sys_raid.1