[Oracle] 測試OracleConnection是否正確關閉

• 若Connection String沒有設定Pooling，預設是開啟(true)。

• 查詢V$Session檢視connection建立情況：OracleConnection.Open()後會建立一connection, 查詢V$Session會出現一筆資料(需以SYSDBA身份登入)
  SELECT SID, USER#, Serial#, audsid, STATUS,
          SchemaName, OsUser, Process, Machine, Program
  FROM V$Session
  WHERE OsUser='Auser'

• 關閉connection, 除了OracleConnection.Close()外, 也需要OracleDataReader.Close()(如果有reader的話), 否則connection無法返還至pool.
  以下例子中, 執行reader.Close()後, V$Session不再有connection的資料,
  若reader.Close()未執行, V$Session會有此connection的資料存在.

        public static void RunSample()

        {

            using (OracleConnection conn =

                new OracleConnection(
                "Data Source=dbserver;User ID=auser;Password=auser;Max Pool Size=3"))

            {

                conn.Open();

                using (OracleCommand comm =
                    new OracleCommand(Settings.GetHostsCmd, conn))

                {

                    OracleDataReader reader = comm.ExecuteReader();

                    while (reader.Read())

                    {

                        Console.WriteLine(string.Format("{0} {1} {2}",

                            reader.GetValue(0),
                            reader.GetValue(1),
                            reader.GetValue(2)));

                    }

                    //reader.Close();

                    Console.WriteLine("Done! ");

                }

            }// 離開using scope, Connection會被close.

            // 移除pool內全部的connection.

            // 若只close connection 沒有close reader,

            // connection沒有返還至pool, 因此無法移除此connection. 

            // 在V$Session可以查詢到此connection.

            OracleConnection.ClearAllPools();

        }