If you search for the Oracle error “Io Exception: The Network Adapter could not establish the connection” (ORA-17002) you will find plenty of discussion on the web. It usually comes down to what the message says, that it is a network issue. But the error can also be caused by e.g. incompatible jar files. In my case, however, I was trying to access a 11g R2 instance from SQL Developer and during initial setup everything had worked. And local access, also with SQL Developer, worked absolutely fine.
Solution: Replace “simple” DB hostname with the fully qualified one. I am not sure why this changed the behavior. I can think of either a DNS setup issue (although my search list included the domain) or some kind of reverse lookup logic that is being applied. Anyway, I wanted to share this finding and also record it for my own future use.
There is an open bug (8930861) with Oracle 11g R2 that causes the Database Configuration Assistent (DBCA) to not start on 32 bit Linux. If you see somthing like
An unexpected error has been detected by HotSpot Virtual Machine:
# SIGSEGV (0xb) at pc=0xa2bbd36e, pid=19555, tid=3085252272
# Java VM: Java HotSpot(TM) Server VM (1.5.0_17-b02 mixed mode)
# Problematic frame:
+# C [libnnz11.so+0x3c36e]+
you have probably hit it. (The above message is copied since I have meanwhile deleted the 32 bit VM. In my case the address was slightly different but the rest of the message was obviously coming from the same underlying reason.) The current workaround is to install on a 64 bit Linux. Given that probably no-one is running a 32 bit version in production these days, this seems acceptable. Also, chances are that this will never be fixed because of the aforementioned lack of 32 bit versions running in production.