Structure_ _Architecture of DBMS.pdf

Structure_ _Architecture of DBMS.pdf

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Copyright @ S t r u c t u r e o f D B M S Data Definition Language Compiler The DDL Compiler converts the data definition statements into a set of tables. These tables contain the metadata concerning the database and are in a form that can be used by other components of DBMS.
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Copyright @ S t r u c t u r e o f D B M S… Data Manager The data manager is the central software component of the DBMS. It is sometimes referred to as the database control system. One of the functions of the data manager is to convert operations in the user’s queries coming directly via the query processor or indirectly via an application program from user’s logical view to a physical file system. The data manager is responsible for interfacing with the file system. In addition, the tasks of enforcing constraints to maintain the consistency and integrity of the data, as well as its security, are also performed by the data manager. Synchronizing the simultaneous operations performed by concurrent users is under the control of the data manager. It is also entrusted with the backup and recovery operations.
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Copyright @ S t r u c t u r e o f D B M S… File Manager Responsibility for the structure of the files and managing the file space rests with the file manager. It is also responsible for locating the block containing the required record, requesting this block from the disk manager, and transmitting the required record to the data manager. The file manager can be implemented using an interface to the existing file subsystem provided by the operating system of the host computer or it can include a file subsystem written especially for DBMS.
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Copyright @ S t r u c t u r e o f D B M S… Disk Manager The disk manager is part of the operating system of the host computer and all physical input and output operations are performed by it. The disk manager transfers the block or page requested by the file manager so that the latter need not be concerned with the physical characteristics of the underlying storage media.
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Copyright @ S t r u c t u r e o f D B M S… Query Processor The database user retrieves data by formulating a query in the data manipulation language provided with the database. The query processor is used to interpret the online user’s query and convert it into an efficient series of operations in a form capable of being sent to the data manager for execution. The query processor uses the data dictionary to find the structure of the relevant portion of the database and uses the information in modifying the query and preparing an optimal plan to access the database.
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Copyright @ S t r u c t u r e o f D B M S… Batch user Data files and data dictionary Telecom System Compiled user interface Compiled application program Naïve user Casual User Telecom system Query Processor DBMS and its data manager OS or own file manager OS disk manager Telecom system DDL Compiler DBA Data files and data dictionary
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