Cannot connect to DB from remote computer (ORA-12545)

Question

Hello all,
Please help, I am stumped.  I am trying to connect to a database located at my work from at home.
I am running into the following issue (see command and error below):
ansichart@ansivm:~/src/perl$ sqlplus aspxdba/********@aspxp2
SQL*Plus: Release 11.2.0.3.0 Production on Thu Jul 18 21:15:09 2013
Copyright (c) 1982, 2011, Oracle.  All rights reserved.
ERROR:
ORA-12545: Connect failed because target host or object does not exist
Here is my tnsnames.ora file (I have the service_name censored out for privacy reasons):
ansichart@ansivm:~/src/perl$ cat $ORACLE_HOME/network/admin/tnsnames.ora
aspxp2 =
  (DESCRIPTION =
    (ADDRESS_LIST =
      (ADDRESS = (PROTOCOL = TCP)(HOST = orarac9-scan)(PORT = 1521))
    (CONNECT_DATA =
      (SERVICE_NAME = *****************)(UR=A)
I have verified that I can establish a TCP connection to this DB server on the port specified, using the same info from the TNSnames.ora file (see below):
ansichart@ansivm:~/src/perl$ nmap -sT -p 1521 orarac9-scan
Starting Nmap 5.21 ( http://nmap.org ) at 2013-07-18 20:53 CDT
Nmap scan report for orarac9-scan (10.1.13.115)
Host is up (0.0088s latency).
PORT     STATE SERVICE
1521/tcp open  oracle
Nmap done: 1 IP address (1 host up) scanned in 0.09 seconds
ansichart@ansivm:~/src/perl$
I have another terminal opened up to a server at work and I can connect to the DB with sqlplus just fine.  I verified that the record for this database on the tnsnames.ora file is the same as it is at work.
In conclusion, I can connect to the Database at work, but I cannot at home, even though I am using the same connection information and verified that port 1521 is accessible on this Database server from at home.  So why can't I establish a DB connection?
Any ideas?
Thanks,
Ben

Answer 1

676d3153-d812-4300-9e6a-b1dc87a2ebfe wrote:
ERROR:
ORA-12545: Connect failed because target host or object does not exist
This simply means "hostname unknown". In other words, the hostname used for the connection could not be resolved to an IP address.
I have verified that I can establish a TCP connection to this DB server on the port specified, using the same info from the TNSnames.ora file (see below):
You are verifying hostname orarac9-scan only. You are not verifying that the hostname supplied by the Oracle SCAN Listener can be resolved by your platform.
As you are connecting to a SCAN listener, it will do its magic (load balancing/round robin/whatever) and return a redirect to your client driver - telling it where to find the service name the client requested.
So your client driver gets a hostname and port in return. It then attempts to connect to that to establish your Oracle client-server session. If the RAC has been setup with the typical RAC hostnames, your client will get hostnames like orarac9-vip1 and orarac9-vip2 returned. Likely as FQDN too.
This means your platform needs to be able to resolve these hostnames. It does not. Thus the error.
In your platform's /etc/hosts file, define the complete list of RAC hostnames (SCAN, Public and VIP hostnames).