ORA-12545: Connect failed because target host or object does not exist - No error on System.Data.OracleClient

Can't believe I am having to ask this question, but I cannot for the life of me connect to an Oracle 11g database.

The following works while using System.Data.OracleClient - but obviously this is depreciated. When using the exact same code but using Oracle.DataAccess.OracleClient I get the following error

{"ORA-12545: Connect failed because target host or object does not exist"}

Here is my code

using (OracleConnection con = new OracleConnection("Data Source=orac;User Id=SYSTEM; Password=Pass;"))
            Console.WriteLine("Connection opened");

            OracleCommand cmd2 = new OracleCommand("SELECT * FROM SYSTEM.TABLE", con);
            OracleDataReader oracleDataReader = cmd2.ExecuteReader();

            while (oracleDataReader.Read())

Could anyone help me out with what I am doing wrong?

I had to change the program to be 32 bit for the Oracle.DataAccess.dll to load.

Is this even the correct library to be using???



tnsnames.ora file as follows:

# tnsnames.ora Network Configuration File: 
# Generated by Oracle configuration tools.

(ADDRESS = (PROTOCOL = TCP)(HOST = localhost)(PORT = 1522))
  (SERVICE_NAME = orac.example.com)

(ADDRESS = (PROTOCOL = TCP)(HOST = localhost)(PORT = 1522))


I have tried connecting using Oracle Sql developer. This works so long as I use the TNS connection type, but doesn't work if I use the Basic connection type.

Also I've noticed that in my services there are 2 called

OracleOraDb11g_home1TNSListener OracleOraDb11g_home2TNSListener

The orac dbhome is home3 I believe, could this be the issue?? If so does anyone know how I would go about fixing it?


UPDATE In HKEY_LOCAL_MACHINE\SOFTWARE\ORACLE\ there are two properties (Default) and inst_loc. There are a few folders two of which are called "KEY_OraDb11g_home1" and "KEY_OraDb11g_home2" these both contain a property called ORACLE_HOME they are:

KEY_OraDb11g_home1 - ORACLE_HOME = C:\app\UserName\product\11.2.0\dbhome_2 KEY_OraDb11g_home2 - ORACLE_HOME = C:\app\UserName\product\11.2.0\dbhome_3

The SID for the Db in home1 is something called OracleDev, I may have installed this at some point long ago, but I certainly don't need it now if it is causing a problem




Let's try something else.

It's possible that ODP.NET doesn't know where to find your Oracle Home because it is not defined in your PATH environment variable, or if it is not set in the registry.

Check your PATH and make sure it contains your Oracle Home directory, and "Oracle Home\bin". For the registry, look for HKEY_LOCAL_MACHINE\SOFTWARE\ORACLE\. In it there should be a key called HOME0 with a string value of ORACLE_HOME. Make sure it points to your Oracle Home.

Check the host file, under C:\windows\system32\drivers\etc, especially if the machine is VM and the IP address of local host might change,if IP address of VM is not static. Change the IP of local host on that file if necessary

Had a similar issue: Visual Studio used the wrong version of tnsnames.ora in ..\11.2.0\client_1\network\admin TNS Ping used the correct version of tnsnames.ora in ..\11.2.0\client_2\network\admin

Hence tnsping was successful but Visual Studio returned: ORA-12545: Connect failed because target host or object does not exist.

Solution, probably not the best one, copied the correct version of tnsnames.ora to ..\11.2.0\client_1\network\admin

I don't know why but setting HOST to in tnsnames.ora and listner.ora worked for me.

Of course, had to run lsnrctl start

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