Esegui i comandi SQL Alter per ogni sessione con Entity Framework 5 parlando con Oracle 11g

puoi usare il metodo Database.Connection.StateChange

    public AtomContext(string nameOrConnectionString)
        : base(nameOrConnectionString)
    {
        this.Database.Connection.StateChange += Connection_StateChange;
    }

    void Connection_StateChange(object sender, StateChangeEventArgs e)
    {
        if (e.OriginalState == ConnectionState.Open || e.CurrentState != ConnectionState.Open)
            return;

        IDbConnection connection = ((EntityConnection)((IObjectContextAdapter)this).ObjectContext.Connection).StoreConnection;
        using (IDbCommand command = connection.CreateCommand("ALTER SESSION SET NLS_LANGUAGE=TURKISH"))
            command.ExecuteNonQuery();

        using (IDbCommand command = connection.CreateCommand("ALTER SESSION SET NLS_COMP = LINGUISTIC"))
            command.ExecuteNonQuery();

        using (IDbCommand command = connection.CreateCommand("ALTER SESSION SET NLS_SORT=TURKISH_AI"))
            command.ExecuteNonQuery();
    }

entityframework ef6 oracle dbcontext session