Use of free space in data and index storage
An important factor that affects how well your table spaces and indexes perform is the amount of available free space. Free space refers to the amount of space that Db2 leaves free in a table space or index when data is loaded or reorganized.
Freeing pages or portions of pages can improve performance, especially for applications that perform high-volume inserts or that update varying-length columns. When you specify a sufficient amount of free space, you trade the amount of used disk space for the performance of certain SQL statements. For example, inserting new rows into free space is faster than splitting index pages.
You use the FREEPAGE and PCTFREE clauses of the CREATE and ALTER TABLESPACE and INDEX statements to set free space values.