The number of Getpage requests per SQL statement
Getpage requests per SQL statement indicate the number of pages that must be accessed for each data row written or read by an application.
Normally, when data rows are read randomly with a unique-key index, one page is read for each index level and one page is read for the data. Typically, the number of pages read to retrieve a data row would be less than six. Similarly, when pages are read sequentially, multiple rows can be retrieved for each page read.
A high Getpage/SQL ratio could be caused by:
- The use of table scan. This causes each page in the table to be accessed and scanned, even though only one row is returned.
- The use of nonmatching index scan. When this happens, one Getpage request is made for each data page in the table and each index page in the associated index, even though only one row is returned.
- The use of an index with low cardinality. This can result in multiple page scans before a row is returned.