cursor threshold option allows you to specify when SQL Server should generate a cursor result set asynchronously. If the optimizer estimates that the number of rows returned by the cursor is greater than the value specified by this parameter, it generates the result set asynchronously. The optimizer makes this decision based on the distribution statistics for each table that is participating in the join in the cursor.
To determine the optimal value for this parameter, you need to make sure that statistics are up-to-date (by running update statistics) for the tables used in the cursors. By default, SQL Server generates a cursor result set synchronously. If you are using a fair number of cursors ...