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Oracle Net Services Problems

The following steps outline what you should always do to diagnose a Oracle Network Services problem, regardless of its nature.
  1. The first step in diagnosing network problems is to obtain the error number from the end user. If the user did not write it down, ask him or her to attempt to re-connect and copy down the error number. More than 80 percent of the time, the error number will take you to the problem. You can display the error text with the "oerr" utility in Oracle. Click to the right of the command prompt to place your cursor there and type oerr ora 12154.
  2. The second step is to try to ping the Oracle server from the client. This can be performed by the DOS ping command or by running the Oracle tnsping utility. Let us try running the tnsping command from a DOS prompt. Click to the right of the command prompt to place your cursor there and type tnsping dilbert.
  3. If you can connect with tnsping, you need to go to the server and verify that the listener is accepting connections. This is done with a loopback command in UNIX. Click your cursor to the right of the command prompt and type sqlplus system/[email protected].
  4. Now you have verified that the server listener is accepting connections and that the WINDOWS client is able to ping the server. The last step is to use SQL*Plus on the client to attempt to connect to the server using the tns service name. Click the next button, and we'll load SQL*Plus for you.
  5. Click in the User Name field to place your cursor there and type system. Then click in the Host String field to place your cursor there and type fred. Click in the Password field and we'll enter your password for you.
  6. Now click OK to connect to the server. This is the end of the simulation.