The issue here could be the load on this system might be different to the others. The applications that run on this system might be different.
If you want to solve the issue, then you got to try first and find out whether you can solve. If successful then spend your time on thinking and contemplating. Its not worth the time of us to provide you any suggestions when you are not ready to test them out!
This is my personal opinion on reading the entire thread once again. Don't think that we are not willing to help. If we need to help you for no cost, then you have to provide us with some test feedbacks. Then only we can eliminate to possibilities.
1. Are you trying to connect to a remote server or is
the db on the same server?
2. IF the db on the same server, did you try increasing the
semaphore limits, reboot the server and then restart the
db and then try?
3. What was the result of PANDO's suggestion?
4. Can you tnsping servicename?
5*. Last call the oraenv and set the environment variable
and try again? In my opinion, its the environment
variable that causeing all the pains. Recheck with
the same server and set. Don't compare with the other
servers as the path might be different from this
1. Db is on the same server.
2. increase semesphoe limit. I didn't tried but how much I should increase? if this value is less then how come i am able to login using oracle unix account.
3.TWO_TASK value is blank.
4.Yes I can tnsping service name.
5. I tried oraenv. Still no luck.
Although I have something new to add:
1. I upgraded the oracle to 18.104.22.168 from 22.214.171.124.
2. My oracle software is installed on /opt/oracle directory.
Which is linked to oracle.
lrwxrwxrwx 1 root other 11 Sep 30 10:42 oracle -> /opt/oracle
$drwxr-xr-x 5 oracle dba 512 Oct 9 20:39 oracle