I prefer to use MSDAORA to connect VB6 to Oracle in large networks. It requires that you provide a server name, userID and password which can be hardcoded in the startup form or retrieved from textboxes. You may want to add a commandTimeout and change the cursor location.

sub CONXMAKE

Set m_ORAconx = New ADODB.Connection
Set m_ORAcmd = New ADODB.Command
Set m_ORArs = New ADODB.Recordset

m_strSQL = _
"data source=" & m_Server & ";" & _
"user id=" & m_UID & ";" & _
"password=" & m_UPW

With m_ORAconx
.Provider = "MSDAORA"
.CursorLocation = adUseClient
.ConnectionTimeout = 3
.ConnectionString = m_strSQL
.Open m_strSQL, , , -1
End With

Set m_ORAcmd.ActiveConnection = m_ORAconx

end sub