The performance provided by an interactive online database system is typically measured in terms of meeting certain pre-specified service level agreements (slas)With expected transaction latency being the most commonly used type of sla. this form of sla acts as a soft deadline for each transaction,And user satisfaction can be measured in terms of minimizing tardiness,that is.the deviation from sla. this objective is further complicated for i/o-intensive transactions,Where the storage system becomes the performance bottleneck. moreover,Common i/o scheduling policies employed by the operating system with a goal of improving i/o throughput or average latency may run counter to optimizing per-transaction performance since the operating system is typically oblivious to the application high-level sla specifications. in this paper,We propose a new sla-aware policy for scheduling i/o requests of database transactions. our proposed policy synergistically combines novel deadline-aware scheduling policies for database transactions with features of operating system scheduling policies designed for improving i/o throughput. this enables our proposed policy to dynamically adapt to workload and consistently provide the best performance.