The issue might be because of an important detail I forgot to mention.
All the servers I’m monitoring, I’ve just pasted there the check_mk_agent. I didn’t installed it. It was just dropped in a path of my choice. This is the reason why I’ve changed the path for these:
export MK_LIBDIR=${MK_LIBDIR:-/usr/lib/check_mk_agent}
export MK_CONFDIR=${MK_CONFDIR:-/etc/check_mk}
export MK_VARDIR=${MK_VARDIR:-/var/lib/check_mk_agent}
Meantime, I’ve got some success when I’ve included mk_oracle code, inside the check_mk_agent code, plus the change that openmindz has referred before.
I don’t know if this is the best or only solution, but is seems to work.
Another important thing to refer, I do not have root access on the servers I’ve to monitor, this was the reason so I’ve not installed the agent and just pasted it there.
Thanks for participating in my question, this is leading me to find out solutions.