Unable to connect using Net service name

Question

I'm running 10.2.0.3 on a RHEL 4 box. I am able to connect to Oracle locally using :
sqlplus username
however, if i try to login using:
sqlplus username@SID, i get this error message:
================================
ERROR:
ORA-01034: ORACLE not available
ORA-27101: shared memory realm does not exist
Linux Error: 2: No such file or directory
==================================
My sqlnet.ora file looks like this:
=======================
SQLNET.AUTHENTICATION_SERVICES=(NONE)
NAMES.DEFAULT_DOMAIN = world
NAMES.DIRECTORY_PATH=(TNSNAMES)
=============================
and my tnsnames.ora file looks like this:
===========================
testsid.world =
(DESCRIPTION =
(ADDRESS_LIST =
(ADDRESS = (PROTOCOL = TCP)(HOST = 1.2.3.4)(PORT = 1521))
(CONNECT_DATA =
(SERVICE_NAME = testsid)
==================================
i ran TNSPING on the box, and that returns a success code, so I'm not really sure what I'm missing here. Any help would be greatly appreciated.

Answer 1

Peculiar.
When you show yourself logging on to an instance, wouldn't it be a good idea to then demonstrate that you've actually connected to the right instance? Instead, you do a mere count from a table. Why not, instead, do a select instance_name, status from v$instance? Then we would indeed know that an instance called TESTSID is running and that its status is OPEN. Without that, your statement that "this is how I know the database is up" is really just a faith-based proposition. The statement you show simply tells us AN instance is up: it doesn't tell us WHICH one, though (and your lsnrctl status feedback makes it clear more than one is running).
Your output from tnsping is largely irrelevant, too. TNSPING tells you whether your client can talk to a listener, and that's it. It says nothing at all about whether the instance you're trying to reach is up, down or otherwise engaged.
A better command to diagnose these sorts of things, incidentally, is lsnrctl services, because it's a service you are ultimately trying to connect to, so seeing what services your listener is aware of is more useful than knowing the status of the listener.
Anyway: your listener has been configured statically to listen for two instances (PBDPASSM and TESTSID). "Configuring statically" means simply that your listener.ora will have a SID_LIST section in which both those services are listed as things the listener should be listening for. Because they're in the SID_LIST, that's why those services are listed in your lsnrctl status report -and that's also why they're listed as status UNKNOWN.
If the instances were actually running, and unless you've set the LOCAL_LISTENER parameter in the init.ora for each instance to something weird, you would **also** see each service listed as 'Ready', because each instance's PMON background process would be registering the existence of its instance dynamically and actively with the listener. It's not saying, "Please listen for this but I don't know if it's running or not" but "here I am and I want you to listen on my behalf". So the listener does know its status at that point, and hence records it as 'ready'.
The fact that you don't have any statuses of 'ready' means the instances aren't running or they are running but unable to register with the listener (perhaps because LOCAL_LISTENER is directing them to some other listener running on another port). But if dynamic registration was not working for that reason, static registration would still be fine for the purposes of making connections if the instance was actually up. Which again raises the question of which one you managed to connect to when you did the sqlplus / as sysdba in your test.
I don't believe the case of anything is the issue here, by the way: your listener reports "testsid" and your SERVICE_NAME is asking for a connection to "testsid", so I see no problem there. It would be different if one said 'TESTSID' and the other 'testsid', but that's not what's happening.
I'd like to see the output of a ps -ef | grep PMON for this host. I'd also like to see the results of a select instance_name, status from v$instance when you do your test connection. And I'd finally like to see the output of show parameter local_listener.