Defines vertical partitioning, horizontal partitioning, or both for the specified table. Horizontal partitioning means that you divide the rows of the table among storage areas according to data values in one or more columns. Vertical partitioning means that you divide the columns of the table among storage areas. A given storage area will then contain only some of the columns of a table. You can combine both horizontal and vertical partitions in a single map. Vertical partitioning reduces disk I/O operations by placing frequently used data in one area, so that you can read and update those portions of the table in a single disk I/O operation. See the Oracle Rdb Guide to Database Design and Definition for more information regarding partitioning.