What is SQL Server deadlock priority and victim selection algorithm?

SQL Server selects a deadlock victim based on cost and optional session priority settings.

When a deadlock occurs, SQL Server evaluates each participating transaction's rollback cost. The transaction with the lowest cost is chosen as the victim. Developers can influence selection using DEADLOCK_PRIORITY. Higher priority sessions are less likely to be chosen as victims. The goal is to minimize rollback work while resolving the cycle quickly.