ORA-00900: Error with opening a session in a SQL statement for Oracle database

Hi all

Maybe someone can help me. 

We have a case where we want to access data from an Oracle DB where we have to open a session before we can execute our query. While this works in other tools, Power BI seems to have a problem (see screenshot)

Our first idea was to create a new query with just the part to open the session and a second one to get the data from the db. This only worked from time to time, when the query to open the session was executed before the second one. Unfortunately, we where not able to solve this problem.

Then we tried to create functions and call them in the right sequence order (see code below). But this dind't work as well.

let
    openSession = () => Oracle.Database("XYZ", [HierarchicalNavigation=true, Query="begin e.env_session_intf#.open_session; end;"]),
    Source = ()  => Oracle.Database("Database", [HierarchicalNavigation=true, Query= "select * from XYZ"]),
    Load = Function.InvokeAfter(openSession, #duration(0,0,0,1)),
    Delay = Function.InvokeAfter(Source, #duration(0,0,0,59)),
    #"Renamed Columns" = Table.RenameColumns(Delay,{{"NAME", "Name"}, {"COMPONENT", "Component"}, {"RELEASE", "Release"}}),
    #"Changed Type" = Table.TransformColumnTypes(#"Renamed Columns",{{"Name", type text}, {"Component", type text}, {"Release", type text}, {"Change ID", type text}}),
    #"Reordered Columns" = Table.ReorderColumns(#"Changed Type",{"Name",  "Component", "Release", "Change ID", "ID"})
in
    #"Reordered Columns"

Any suggestions how this could work? Maybe someone already has experience with this problem.

Thanks a lot!