Research And Implementation Of Relational Database Storage Subsystem

DBMS's storage subsystem is responsible for the disk and the main memory control, which contacts with the file system or the original equipment alternately, dispatches data moving between disk and main memory, translates different DDL and DML statement to the lower level file system command or the device operation command and completes data storage, select and update in the database.The design and implementation of storage subsystem has very important influence to the database performance. The paper is based on opensource database Postgresql,uses tablespace mode to implement data storage subsystem strategy, the main achievement and conclusions are: (1)Obtained the PostgreSQL system structure based on the PostgreSQL development documents and source code, then proposed SMS and DMS coexistence tablespace storage strategy to make DBA choose appropriate storage structure based on actual application environment conveniently. (2) Designed and implemented the DMS tablespace storage strategy, satisfied the requirements: store data in multiple disks, layout database metadata and data storage location reasonably and enhanced disk I/O efficiency. (3) Has profited from the Oracle automated segment space management mode, used bitmap to manage segment space, could manage free block and extend segment rapidly and efficiently. (4)Integrated DMS tablespace storage strategy into the original PostgreSQL system, modified the data dictionary,buffer pool management and transaction log and so on to guarantee the system run normally, and implemented shared mode data dictionary cache buffer to reduce main memory usage and reduce process communication burden. (5)Implemented dynamic performance view by virtue of PostgreSQL original function to collect statistical information to make DBA optimize storage structure conveniently.