allow backward scans

Summary information

Default value

1 (on)

Valid values

0 (off), 1 (on)

Status

Dynamic

Display level

Intermediate

Required role

System Administrator

allow backward scans controls how the optimizer performs select queries that contain the order by...desc command:

The first method—performing backward scans—can speed access to tables that need results ordered by descending column values. Some applications, however, may experience deadlocks due to backward scans. In particular, look for increased deadlocking if you have delete or update queries that scan forward using the same index. There may also be deadlocks due to page splits in the index.

You can use print deadlock information to send messages about deadlocks to the error log. See “print deadlock information”. Alternatively, you can use sp_sysmon to check for deadlocking. See the Performance and Tuning Guide for more information on deadlocks.