You always need to push the checkmk config directory if you run the plugin standalone:
MK_CONFDIR=/etc/check_mk/ /usr/lib/check_mk_agent/plugins/mk_oracle -t
(Please always run this command exactly as above, any other execution won’t work)
This is the only way how checkmk can find your installation and can set the environment to work as root.
Seems like your listener is not running?
Seems like you have defined a wrong connection in your config file?
it should be look something like
DBUSER='<user>:<password>:<role>:<dbhost>:<listenerport>'
ASMUSER='<user>:<password>:<role>:<dbhost>:<listenerport>'
For ASM you probably need to connect as SYSDBA role. Keep in mind in default installation you only can query your ASM instance from the local node if you are running a cluster.
Please always use the preformatted text option of the forum to preserve the special characters and give as a bit more readable text boxes.