The number of entries and elements in a structure is a function of the attributes specified at connect time. The structure alter function can change the ratio of entries to elements in a structure. The request to change the entry-to-element ratio is limited by the composite RATIO, MINENTRY, and MINELEMENT values.

A request to alter the size of a structure (expand or contract) might also result in a change to the entry-to-element ratio of the structure. When a structure is allocated initially, the system determines the target entry-to-element ratio and attempts to allocate the number of entries and elements accordingly. If the target ratio cannot be satisfied, the system maintains the current count of entries and elements along with the original target ratio. When an IXLALTER request is received to expand or contract the structure size, the system checks the current entry and element counts to determine if the current entry-to-element ratio equals the original target ratio. If the current ratio is not the same as the target ratio, the system uses the target ratio to calculate the target entry and element counts that will be used when altering the structure's size.