Re: Could not Login into ORACLE

Following is my high level (verbal) flowchart for Oracle Networking that I use for troubleshotsing. Appreciate any corrections and significant enhancements (that do not expand it too much)

Roughly, the most common scenario (as there are many variants) is:

Part A) Establishing communication in the first place

Client (sqlplus)
- talks to Oracle Networking client-side

        looks up the target service in the local (client's) tnsnames.ora
- which talks to TCP/IP,

• which talks to the server's Listener (on port 1521) looks up the instance (if not self registered) in listener.ora
• which tells the instance to talk to the client (on port xyz)

Part b) Keeping communication

Client
- talks to Oracle Networking client-side

• which talks to TCP/IP
• which talks to instance's 'user process' on port xyz resolves the request through the 'instance' (SGA)
• which answers using the same path in reverse.

Your question could be easier answered if you posted the exact message, but I suspect one of

• you have not even specified a service in the tnsnames.ora OR
• your tnsnames.ora file is not setup correctly on the client running sqlplus (the @service is the index into tnsnames.ora) OR
• your listener on the server is not up

Another possibility, the instance is not registered to the listener, does not appear to happen right now.

/Hans Received on Mon Aug 30 2004 - 08:49:51 CDT