Earning Points. Starwood's Preferred Guest program is fairly straightforward: the more nights you spend at participating hotels, the faster you'll earn a free night.
As seen in the EXECUTING phase, the map will write (using Mapper.Context.write()) its output into a circular in-memory buffer (MapTask.MapOutputBuffer). The size of this buffer is fixed and determined by the configuration parameter mapreduce.task.io.sort.mb (default: 100MB).
The mapper output (intermediate data) is stored on the Local file system (NOT HDFS) of each individual mapper nodes. This is typically a temporary directory location which can be setup in config by the hadoop administrator. The intermediate data is cleaned up after the Hadoop Job completes.