class Program
{
  static void Main()
  {
    var sw = new Stopwatch();
    sw.Start();
    using (var cnn = new OracleConnection("User Id=scott;Password=tiger"))
    using (var cmd = new OracleCommand("select * from all_objects where owner='SYS'", cnn))
    {
      cnn.Open();
      using (var reader = cmd.ExecuteReader())
        Copy(reader);
    }
    sw.Stop();
    Console.WriteLine(sw.Elapsed);
    Console.WriteLine("done");
    Console.ReadKey(true);
  }

  static void Copy(DbDataReader reader)
  {
    var ddl = GetTableDdl(reader);
    using (var cnn = new SqlConnection("Data Source=.;Initial Catalog=stuff;Integrated Security=True"))
    using (var cmd = new SqlCommand(ddl, cnn))
    {
      cnn.Open();
      cmd.ExecuteNonQuery();
      using (var bc = new SqlBulkCopy(cnn))
      {
        bc.DestinationTableName = "dbo.MyTable";
        bc.WriteToServer(reader);
      }
    }
  }

  static string GetTableDdl(IDataReader reader)
  {
    var schema = reader.GetSchemaTable();
    if (schema == null)
      throw new ApplicationException("Schema table is null");
    var sb = new StringBuilder();
    sb.Append("create table dbo.MyTable (");
    foreach (DataRow row in schema.Rows)
      sb.Append(Environment.NewLine)
        .Append("\t")
        .Append("[")
        .Append(row["ColumnName"])
        .Append("] ")
        .Append(GetTypeById((OracleDbType)row["ProviderType"]))
        .Append(GetColumnSize(row))
        .Append((bool)row["AllowDBNull"] ? string.Empty : " NOT NULL")
        .Append(",");
    sb.Length -= 1;
    sb.Append(Environment.NewLine).Append(")");
    return sb.ToString();
  }

  static string GetTypeById(OracleDbType type)
  {
    switch(type)
    {
      case OracleDbType.Date:
        return "datetime";
      case OracleDbType.Decimal:
        return "float";
      case OracleDbType.Varchar2:
        return "varchar";
      case OracleDbType.NVarchar2:
        return "nvarchar";
      case OracleDbType.Clob:
        return "varchar(max)";
      case OracleDbType.NClob:
        return "nvarchar(max)";
      case OracleDbType.Blob:
        return "varbinary(max)";
      // итд итп
      default:
        throw new ArgumentException($"Unsupported type: {type}");
    }
  }

  static string GetColumnSize(DataRow row)
  {
    var type = (OracleDbType) row["ProviderType"];
    switch(type)
    {
      case OracleDbType.Date:
      case OracleDbType.Clob:
      case OracleDbType.NClob:
      case OracleDbType.Blob:
      case OracleDbType.Decimal:
        return string.Empty;
      case OracleDbType.Varchar2:
      case OracleDbType.NVarchar2:
        return string.Concat("(", row["ColumnSize"], ")");
      default:
        throw new ArgumentException($"Unsupported type: {type}");
    }
  }
}

00:00:06.6274468
done

use [stuff]
go
SELECT 
  p.rows AS RowCounts,
  sum(a.used_pages)*8 UsedSpaceKB
FROM sys.tables t
inner join sys.indexes i on i.object_id=t.object_id
inner join sys.partitions p on p.object_id=i.object_id and p.index_id=i.index_id
inner join sys.allocation_units a on a.container_id=p.partition_id
left outer join sys.schemas s on t.schema_id = s.schema_id
where t.object_id=object_id(N'dbo.MyTable')
group by p.rows

RowCounts            UsedSpaceKB
-------------------- --------------------
34434                4584

(1 row(s) affected)