We have installed Oracle 11g in our system. We were able to connect to the database instance, sql plus and all. Suddenly yesterday onwards we were not able to connect to the instance. It is throwing error such as
"An error was encountered performing the requested operation:
The Network Adapter could not establish the connection
Vendor code 20"
I have found many solutions for the same in the net such as
1) Run the listener service again (Already it is running in windows services. Even if I restarted it, no use)
2)Adding the user_dedicated_server=ON in sqlnet.ora for the server which is mentioned as SERVER = DEDICATED in tnsnames.ora file
3)Not able to open sql plus or start the listener from command prompt. (its throwing error Message 1070 not found; No message file for product=NETWORK, facility=TNSTNS-12557: Message 12557 not found; No message file for product=NETWORK, facility=TNS
TNS-12560: Message 12560 not found; No message file for product=NETWORK, facility=TNS
TNS-00527: Message 527 not found; No message file for product=NETWORK, facility=TNS)
4)In oracle enterprise manager, its showing the error for the agent connection such as
Details ORA-12541: TNS:no listener (DBD ERROR: OCIServerAttach)
Is this behavior specific to using Oracle Providers for ASP.NET? Are you able to connect via sqlplus from the same client machine? If this is a basic client connectivity issue unrelated to the ASPNET providers, you'll probably want to post in a different forum. What behavior do you get if you try to connect from SQLPlus?