The “Index Scans” section reports forward and backward scans by lock scheme:
“Ascending Scans” reports the number of forward scans on allpages-locked tables.
“DOL Ascending Scans” reports the number of forward scans on data-only-locked tables.
“Descending Scans” reports the number of backward scans on allpages-locked tables.
“DOL Descending Scans” reports the number of backward scans on data-only-locked tables.
For more information on forward and backward scans, see “Costing for queries using order by” on page 77 in Performance and Tuning: Optimizer.
