“Updates” reports the number of deferred and direct row updates. The “% of total” column reports the percentage of each type of update as a percentage of the total number of row updates. sp_sysmon reports the following types of updates:
APL Deferred
APL Direct In-place
APL Direct Cheap
APL Direct Expensive
DOL Deferred
DOL Direct
Direct updates incur less overhead than deferred updates and are generally faster because they limit the number of log scans, reduce locking, save traversal of index B-trees (reducing lock contention), and can save I/O because Adaptive Server does not have to refetch pages to perform modification based on log records.
For a description of update types, see “How update operations are performed” on page 92 in Performance and Tuning: Optimizer.
If there is a high percentage of deferred updates, see “Optimizing updates” on page 100 of the same book.
“Total Rows Updated” reports all deferred and direct updates combined. The “% of total” columns shows the percentage of rows updated, based on all rows modified.
