Overflow Chains and Locking
Tables with overflow pages can cause locking problems because all pages in the overflow chain must be locked when a row in the chain is accessed.
Escalation to table-level locking while locking an overflow chain can cause deadlock. If you have a table with many overflow pages that are still present after a modify, either increase the table page size to allow more rows on a page or use the SET LOCKMODE statement as follows:
• Establish table-level locking as the default for that table
• Increase MAXLOCKS