SQL and Access Paths › Access Paths › Table space Scans

Table space Scans

You can use the DB2 table space scan to search an entire table space to satisfy a query. The type of table space determines what is scanned. Simple table spaces will be scanned in their entirety. Segmented and universal table spaces will be scanned for only the table specified in the query.

Note: An R in the PLAN_TABLE ACCESSTYPE column indicates a table space.

A table space scan is selected as an access method when:

• A matching index scan is not possible because no index is available or no predicates match the index column.
• DB2 calculates that a high percentage of rows is retrieved, so any index access would not be beneficial.
• The indexes that have matching predicates have a low cluster ratio and are not efficient for large amounts of data that the query is requesting.