Page Splits

Number of page splits for data pages, clustered index pages, or nonclustered index pages that occurred because there was not enough room for a new row.

When a data row is inserted into an allpages-locked table with a clustered index, the row must be placed in physical order according to the key value. Index rows must also be placed in physical order on the pages. If there is not enough room on a page for a new row, Adaptive Server splits the page, allocates a new page, and moves some rows to the new page. Page splitting incurs overhead because it updates the parent index page and the page pointers on the adjoining pages and adds lock contention. For clustered indexes, page splitting also updates all nonclustered indexes that point to the rows on the new page.

See Chapter 5, “Indexes,” in Performance and Tuning Series: Locking and Concurrency Control for more information.