INF: Detecting Deadlocks

ID Number: Q45548

1.00 1.10 1.11 4.20

OS/2

Summary:

SQL Server cannot detect deadlocks by simple timeout. SQL Server keeps

track of which locks belong to which processes. When a request for a

lock is blocked by another process that already holds a lock on that

object, SQL Server checks to see if that other process is waiting for

a lock that belongs to this process. In fact, it checks all waiting

processes so that even transitive deadlocks are detected.

Deadlock does not refer to one transaction waiting for another to

release a lock; it refers to a closed loop of waiting processes.

Because it is impossible for any of the processes to ever complete, a

timeout period makes no sense. Once the condition is detected, the

process with the least amount of time invested is terminated.

Additional reference words: 1.00 1.10 1.11 4.20