Recovery performance in the event of failures is very important for distributed real-time database systems. This paper presents a time-cognizant logging-based crash recovery scheme （TCLCRS） that aims at distributed ...Recovery performance in the event of failures is very important for distributed real-time database systems. This paper presents a time-cognizant logging-based crash recovery scheme （TCLCRS） that aims at distributed real-time databases, which adopts a main memory database as its ground support. In our scheme, each site maintains a real-time log for local transactions and the subtransactions, which execute at the site, and execte local checkpointing independently. Log records are stored in non-volatile high- speed store, which is divided into four different partitions based on transaction classes. During restart recovery after a site crash, partitioned crash recovery strategy is adopted to ensure that the site can be brought up before the entire local secondary database is reloaded in main memory. The partitioned crash recovery strategy not only guarantees the internal consistency to be recovered, but also guarantee the temporal consistency and recovery of the sates of physical world influenced by uncommitted transactions. Combined with two- phase commit protocol, TCLCRS can guarantee failure atomicity of distributed real-time transactions.展开更多
Many existing real time commit protocols try to improve system performance by allowing a committing cohort to lend its data to an executing cohort, thus reducing data inaccessibility. They block the borrower from send...Many existing real time commit protocols try to improve system performance by allowing a committing cohort to lend its data to an executing cohort, thus reducing data inaccessibility. They block the borrower from sending WORKDONE/PREPARED message and restrict them from lending data so that transaction abort chain is limited to one. Thus, transaction execution time increases. This paper proposes a modified real time commit protocol for distributed real time database systems (DRTDBS), Allow Commit Dependent and in Time borrowers for Incredible Value added data lending without extended abort chain (ACTIVE), where borrower cohorts are categorized as commit and abort dependent. Further, the commit dependent borrowers can lend data to executing cohorts with still limiting the transaction abort chain to one only and reducing the data inaccessibility. Also, an incoming executing cohort having borrowing factor greater than one can only borrow the dirty data items from lender. This minimizes the fruitless borrowing by the cohort. The performance of ACTIVE is compared with PROMPT, 2SC and SWIFT protocols for both main memory resident and disk resident databases with and without communication delay. Simulation results show that the proposed protocol improves the system performance up to 4% as transaction miss percentage.展开更多
基金Project supported by National Natural Science Foundation ofChina (Grant No .60203017) Defense Pre-research Projectof the"Tenth Five-Year-Plan"of China (Grant No .413150403)
文摘Recovery performance in the event of failures is very important for distributed real-time database systems. This paper presents a time-cognizant logging-based crash recovery scheme （TCLCRS） that aims at distributed real-time databases, which adopts a main memory database as its ground support. In our scheme, each site maintains a real-time log for local transactions and the subtransactions, which execute at the site, and execte local checkpointing independently. Log records are stored in non-volatile high- speed store, which is divided into four different partitions based on transaction classes. During restart recovery after a site crash, partitioned crash recovery strategy is adopted to ensure that the site can be brought up before the entire local secondary database is reloaded in main memory. The partitioned crash recovery strategy not only guarantees the internal consistency to be recovered, but also guarantee the temporal consistency and recovery of the sates of physical world influenced by uncommitted transactions. Combined with two- phase commit protocol, TCLCRS can guarantee failure atomicity of distributed real-time transactions.
文摘Many existing real time commit protocols try to improve system performance by allowing a committing cohort to lend its data to an executing cohort, thus reducing data inaccessibility. They block the borrower from sending WORKDONE/PREPARED message and restrict them from lending data so that transaction abort chain is limited to one. Thus, transaction execution time increases. This paper proposes a modified real time commit protocol for distributed real time database systems (DRTDBS), Allow Commit Dependent and in Time borrowers for Incredible Value added data lending without extended abort chain (ACTIVE), where borrower cohorts are categorized as commit and abort dependent. Further, the commit dependent borrowers can lend data to executing cohorts with still limiting the transaction abort chain to one only and reducing the data inaccessibility. Also, an incoming executing cohort having borrowing factor greater than one can only borrow the dirty data items from lender. This minimizes the fruitless borrowing by the cohort. The performance of ACTIVE is compared with PROMPT, 2SC and SWIFT protocols for both main memory resident and disk resident databases with and without communication delay. Simulation results show that the proposed protocol improves the system performance up to 4% as transaction miss percentage.
