Connecting to an Oracle server you know is there. But connection still fails. What gives.

Article
11/06/2008

For some reason I have lately got a few cases related to connecting to Oracle.

All seems to be well in terms of Oracle being up and running etc, but still the client can't connect.

To add to the confusion, there are different errors depending on how you (try) to connect to the Oracle server.

I'll show you three ways of connecting, and their respective error messages. So, for the sake of showing the different errors, we have 3 clients.

Client 1 - A .Net application with the System.Data.OracleClient classes:

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static void Main(string[] args)

{

string cStr = @"Data Source=<server>;User Id=<user>;Password=<password>";

using (OracleConnection oc = new OracleConnection(cStr))

{

try

{

oc.Open();

oc.Close();

}

catch (Exception ex)

{

Console.WriteLine(ex);

}

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Client 2 - An old school vbscript file (*.vbs) client:

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WScript.Echo "Connecting..."

Dim con

set con = CreateObject("ADODB.Connection")

con.Open "Provider=MSDAORA;Data Source=<server>;User ID=<user>;Password=<password>"

WScript.Echo "Connected, now closing"

con.Close

WScript.Echo "Done!"

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Client 3 - A plain UDL.

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- Create a .txt on the desktop.

- Rename it to Test.udl

- Click it and fill in the details like so:

Provider : Microsoft OLE DB Provider for Oracle

Server : <your server>

User Name : <your username>

Password : <your password>

- Now click "Test Connection"

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The reason for having 3 clients is, as mentioned, that they all, annoyingly enough, shows somewhat different errors even thought the problem is the same.

So, these are the scenarios and the errors, for both scenarios you are trying to connect to your Oracle server, but receive the following errors:

Scenario 1:

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Client 1 gives:

System.Exception: OCIEnvCreate failed with return code -1 but error message text was not available.

at System.Data.OracleClient.OciHandle..ctor(OciHandle parentHandle, HTYPE handleType, MODE ocimode, HANDLEFLAG handleflags)

at System.Data.OracleClient.OracleInternalConnection.OpenOnLocalTransaction(String userName, String password, String serverName, Boolean integratedSecurity, Boolean unicode, Boolean omitOracleConnectionName)

at System.Data.OracleClient.OracleInternalConnection..ctor(OracleConnectionString connectionOptions)

at System.Data.OracleClient.OracleConnectionFactory.CreateConnection(DbConnectionOptions options, Object poolGroupProviderInfo, DbConnectionPool pool, DbConnection owningObject)

at System.Data.ProviderBase.DbConnectionFactory.CreatePooledConnection(DbConnection owningConnection, DbConnectionPool pool, DbConnectionOptions options)

at System.Data.ProviderBase.DbConnectionPool.CreateObject(DbConnection owningObject)

at System.Data.ProviderBase.DbConnectionPool.UserCreateRequest(DbConnection owningObject)

at System.Data.ProviderBase.DbConnectionPool.GetConnection(DbConnection owningObject)

at System.Data.ProviderBase.DbConnectionFactory.GetConnection(DbConnection owningConnection)

at System.Data.ProviderBase.DbConnectionClosed.OpenConnection(DbConnection outerConnection, DbConnectionFactory connectionFactory)

at System.Data.OracleClient.OracleConnection.Open()

Client 2 gives:

Microsoft OLE DB Provider for Oracle: Oracle error occurred, but error message could not be retrieved from Oracle.

Client 3 gives:

Test connection failed because of an error in initializing provider. Oracle error occurred, but error message could not be retrieved from Oracle.

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Scenario 2:

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Client 1:

System.Exception: System.Data.OracleClient requires Oracle client software version 8.1.7 or greater.

at System.Data.OracleClient.OCI.DetermineClientVersion()