Zone maps

Zone maps are automatically generated internal tables. They're used to improve the throughput and response time of SQL queries against large grouped or nearly ordered date, timestamp, byteint, smallint, integer, and bigint data types.

Zone maps reduce disk scan operations that are required to retrieve data by eliminating records outside the start and end range of a WHERE clause on restricted scan queries. The Storage Manager uses zone maps to skip portions of tables that do not contain rows of interest and thus reduces the number of disk pages and extents to scan and the search time, disk contention, and disk I/O.

You can use column-oriented or table-oriented zone maps. Use a column-oriented zone map structure where all zone map statistics for the same column number across all tables are stored together in the data slice. Table-oriented zone maps are optimized for improved performance of incremental (or trickle) loads. Table-oriented zone maps also minimize interactions between concurrent loads to a subset of tables in the system, from queries running against a different subset of tables.

Automatically create zone maps and refresh existing zone maps on each data slice when you insert, update, load data into tables, or generate statistics.