Hello,
We had a very strange problem in connection to Oracle 12.1.0.1 database on AIX 7.1 server.
While connecting to database with sqlplus username/password@SID was taking minutes to get connection, also response from tnsping was delayed as well as listener was taking time to start/stop.
This was not the case few weeks back.
Response from Server itself was quick, all commands, OS operations were normal (speed), only sqlplus/tnsping operations were getting delayed. After connection database performance was also normal. IT had ruled out any possibility of network issues.
On detailed investigation we found there was something wrong with one of the DNS server listed in /etc/resolv.conf, we have three DNS server and this not working server is third one. Though nslookup <servername> was quick enough to return host information (not from this failed DNS server).
When we removed this failed DNS server entry from /etc/resolv.conf, sqlplus and tnsping started performing well also listenere start/stop speed was improved.
So wanted to know why this wrong DNS server was creating problem when two other DNS servers were able to resolve name.
How listener/sqlplus connection/tnsping gets impacted even if one DNS server do not work properly.
Thank you,
Kishor