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