The Design And Implementation Of Backup And Recovery Subsystem In DaMeng Database

Some unexpected hardware or software failure may influence the correct running of transaction of DBMS,even destory the database,which will descrease the reliability and availability of DBMS。The part of backup and recovery in DBMS is to solve these problems。We have a deep research on backup and recovery teniques in the context of DM4,and design a backup and recovery subsystem to cope with the three classical database failures,which include transaction failure,system failure and media failure。The backup and recovery subsystem in DM4 has multiple backup modes and recovery tecnique based on REDO log,rollback segment and action consistent checkpoint。The REDO log records the modified data of transaction and the UNDO log in the rollback segment records the previous data,which collect enough information for the recovery。The periodic action consistent checkpoint flushs the dirty pages in buffer into databases and log files,which provides the latest recovery point and decreases the recovery time。When the transaction failure occurs,we rollback the UNDO log records in the rollback segment to undo the uncommitted transactions,which keeps the atomicity of the transaction and implements the transaction recovery。When system failure occurs,we use the REDO log records to "repeat the history" from the latest checkpoint record in REDO log files,then undo the uncommitted transaction by rolling back the UNDO log records in the rollback segment,which insures the atomicity and durability of the transactions and the consistency of databases,and implements the system recovery。When media failure occurs,we restore the database to a backup state by the copy of backup,then recovery the database by the system recovery tenique,which solves the media failure and implements media recovery。The copy of backup is acquired by the backup procedure,and we provide multiple backup modes such as offline backup,online backup,full backup and incremental backup。We adopts the multiple-thread tenique to decrease the time of online backup and better the effiency。...