Parallel clustered index partition scan (allpages-locked tables)

A clustered index partition scan uses multiple worker processes to scan data pages in a partitioned table when the clustered index key matches a search argument. This method can be used only on allpages-locked tables.

One worker process is assigned to each partition in the table. Each worker process accesses data pages in the partition, using one of two methods, depending on the range of key values accessed by the process. When a partitioned table has a clustered index, rows are assigned to partitions based on the clustered index key.

Figure 25-2 shows a clustered index partition scan that spans three partitions. Worker processes A, B, and C are assigned to each of the table’s three partitions. The scan involves two methods: