The 'Half-

In this paper, we propose locking protocols that are useful for real-time databases. Our approach is motivated from two main observations. First, locking protocols are widely accepted and used in most database systems. Second, in real-time databases it has been shown that the blocking behavior of transactions in locking protocols results in performance degradation. We use a new relationship between locks called ordered sharing to eliminate blocking that arises in the traditional locking protocols. Ordered sharing eliminates blocking of read and write operations but may result in delayed commitment. Since in real-time databases, timeliness and not response time is the crucial factor, or protocols exploit this delay to allow transactions to execute within the slacks of delayed transactions. We compare the performance of the proposed protocols with the two phase locking protocol for real-time databases. Our experiments indicate that the propose protocols significantly reduce the percentage of missed deadlines in the system for a variety of workloads.