| 摘要 |
PURPOSE:To avoid a deadlock by sequentially checking whether the transaction set of a list is a zero set or not, judging the presence or absence of the occurrence of the deadlock, giving a lock permission when there is no possibility of the occurrence of the deadlock and giving the unpermission of a lock when there is the possibility of the occurrence of the deadlock. CONSTITUTION:A transaction T2 can lock a file F2. Namely, a transaction T1 executes a lock reservation, but the transaction set is the zero set since {U'}=PHI (zero set). On the other hand, the transaction T1 cannot lock the file F2. The cause is that {U'} T2 and at the same time, {U'} T2, namely, the transaction T2 lock-reserves the file F2 and locks the file F2. The similar processing is executed in a subsequent schedule. Thus, the file can be accessed without the deadlock irrespective of a stamp time.
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