A deadlock can occur when two or more users are waiting for data locked by each
other. Deadlocks prevent some transactions from continuing to work. Figure 13–3 is a
hypothetical illustration of two transactions in a deadlock.
In Figure 13–3, no problem exists at time point A, as each transaction has a row lock on
the row it attempts to update. Each transaction proceeds without being terminated.
However, each tries next to update the row currently held by the other transaction.
Therefore, a deadlock results at time point B, because neither transaction can obtain
the resource it needs to proceed or terminate. It is a deadlock because no matter how
long each transaction waits, the conflicting locks are held.
1. 当两个用户互相等待对方释放锁定的资源时就会发生死锁 , 死锁将阻止事务继续执行
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