The zone map in Netezza is similar (concept-wise) to partitions in Oracle. Netezza maintains a map for data so that it does rely on a zone map to pull only the range it is interested in.
For example, if we need to pull out data from Jan 2009 till June 2009 from a table that is distributed on the date column, the zone map helps us to achieve this. The zone map is maintained by Netezza automatically, no user intervention needed. Zone mapping is done at a block (extent) level. Netezza has zone maps for all columns (not just distributed columns) and includes information such as minimum, the maximum, total number of records.
