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Access Oracle without tnsnames.ora

, 4 Nov 2005
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How to access Oracle without tnsnames.ora.

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Have you ever tried to access an Oracle instance from VBScript? It is not too complicated, but normally you need an additional file called tnsnames.ora in the Oracle installation directory. This article describes an easy way to access an Oracle instance without this file. All you have to do is use a different connection string.

Using the code

You can use this kind of connection strings from VBScript, VBA and Visual Basic. I also tested it with Perl, it worked. Using a connection string without the need to have a correct tnsname.ora on your computer is especially useful for ad hoc scripting on many different database instances, or when you are not sure if the user has a correct tnsnames.ora on his computer.

First take a look at the standard connection string for Oracle, used in a VBScript file:

Dim strCon
strCon = "Driver={Microsoft ODBC for Oracle}; " & _
         "CONNECTSTRING=MYDB; uid=read;pwd=read;"

You see in the first section the driver name (Microsoft ODBC for Oracle), followed by the alias for the instance, and last the Oracle username and password. The alias name MYDB also needs a corresponding entry in the file tnsnames.ora. Mostly you will find this file in the following directory: <Oracle-Home>\network\admin. In this file you need a definition of the alias:

      (ADDRESS = (PROTOCOL = TCP)(HOST = mysrv)(PORT = 7001))

Oracle uses this definition to determine which physical database instance is associated with the given alias MYDB. This is why we need the file tnsnames.ora when we access an Oracle instance. But is this necessary? No, not really! All you have to change: include the physical connection data (like host and port) in your connection string. Here is the modified connection string in VBScript:

Dim strCon
strCon = "Driver={Microsoft ODBC for Oracle}; " & _
         "(ADDRESS=(PROTOCOL=TCP)" & _
         "(HOST=mysrv)(PORT=7001))" & _
         "(CONNECT_DATA=(SERVICE_NAME=MYDB))); uid=read;pwd=read;"

Now you will be able to access every Oracle instance, without the need to have a correct tnsnames.ora on your client machine. Finally here is the complete source code that selects some rows and writes them to STDOUT:

Dim strCon
strCon = "Driver={Microsoft ODBC for Oracle}; " & _
         "(ADDRESS=(PROTOCOL=TCP)" & _
         "(HOST=mysrv)(PORT=7001))" & _
         "(CONNECT_DATA=(SERVICE_NAME=MYDB))); uid=read;pwd=read;"

Dim oCon: Set oCon = WScript.CreateObject("ADODB.Connection")
Dim oRs: Set oRs = WScript.CreateObject("ADODB.Recordset")
oCon.Open strCon
Set oRs = oCon.Execute("SELECT myfield FROM mytable)
While Not oRs.EOF
    WSCript.Echo oRs.Fields(0).Value
Set oRs = Nothing
Set oCon = Nothing

I hope that you find this article useful. For me this kind of a connection string is useful, when I cannot be sure if the end-user had a correct tnsnames.ora on his computer.


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About the Author

Web Developer
Germany Germany
Florian works as consultant for change- and configuration management for about 7 years. In this environment he is often forced to work with unix, perl and shell scripts.
For more information about change- and configuration management (espacially Serena Dimensions) visit:
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Comments and Discussions

GeneralRetrieve / Insert XML (or txt) file in Oracle Pinmember2Shaar26-Feb-09 7:25 
GeneralCheck whether Oracle Client is installed Pinmemberswanand_rk21-Nov-07 4:06 
QuestionOracle Connection Manager Pinmembertrberube12-Apr-07 7:01 
GeneralOracle Connectivity from VBscript Pinmemberbinimol3-Apr-07 20:46 
GeneralRe: Oracle Connectivity from VBscript Pinmemberfstrahberger4-Apr-07 0:49 
GeneralRe: Oracle Connectivity from VBscript Pinmemberbsatishus4-Apr-07 4:04 
GeneralRe: Oracle Connectivity from VBscript Pinmemberfstrahberger4-Apr-07 5:16 
GeneralRe: Oracle Connectivity from VBscript Pinmemberbsatishus4-Apr-07 11:27 
GeneralRe: Oracle Connectivity from VBscript PinmemberLonestar.org1-Oct-10 22:01 
GeneralORA-12154 PinmemberPasNad17-Oct-06 2:32 
GeneralRe: ORA-12154 Pinmemberfstrahberger17-Oct-06 2:54 
GeneralRe: ORA-12154 PinmemberPasNad17-Oct-06 17:14 
GeneralRe: ORA-12154 Pinmemberfstrahberger17-Oct-06 20:30 
QuestionOther providers PinmemberYoniP21-Nov-05 1:24 
QuestionWhy? PinmemberPatrice Borne4-Nov-05 13:20 
AnswerRe: Why? Pinmemberfstrahberger5-Nov-05 13:39 
Hi Patrice,
I perfectly agree that this way is not the most elegant solution to connect to oracle. But it is a easy solution, when you have no control, what happens on your customers computers.
In some environments you can not be shure wether the file tnsnames.ora is correct or not. In this cases the connection to oracle will work, even if the configuration on the client-computer is not ok (old tnsnames.ora, wrong oracle home, ...).
Another thing is "ad hoc scripting and reporting". We have many different oracle instances (they also change over the time) in our environment (and I don't have write access to the oracle-home directory). Using the physical connection parameters, I can connect to every instance without the need to have it in my tnsnames.ora. It also works with the oracle tools like sqlplus:
So: I don't recommend to use this connection string - but it is a way, when you have no other solution to connect to an instance.

-- modified at 18:39 Saturday 5th November, 2005
GeneralRe: Why? PinmemberCastorTiu12-Nov-05 23:08 

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