The following lines are included only for partitioned tables. They give the number of partitions, plus the number of pages in the largest partition, and the skew:
The table has 5 partitions. The largest partition has 211 pages. The partition skew is 1.406667.
This information is useful if you are tuning parallel queries, because:
Costing for parallel queries is based on the cost of accessing the table’s largest partition.
The optimizer does not choose a parallel plan if the partition skew is 2.0 or greater.
See Chapter 24, “Parallel Query Processing,” for more information on parallel query optimization.