title: RDD transformation and actions
body: <p>While doing transformations on RDD, for example :-</p>
  
  <pre><code>firstRDD=spark.textFile("hdfs://...") 
  
  secondRDD=firstRDD.filter(someFunction);
  
  thirdRDD = secondRDD.map(someFunction);
  </code></pre>
  
  <p>Does first, second and third RDD store the value in RAM or when we perform action on the final thirdRDD like <code>result = thirdRDD.count()</code> then it will store the data?</p>