The storage manager is a key component of a database system that is responsible for managing the storage of data on secondary storage devices, such as hard disks, solid-state drives, and tape drives. It provides an interface between the database system and the operating system, translating data requests from the query processor into low-level file system operations.
The storage manager has two main responsibilities: managing the physical storage of data on disk, and managing access to the data by the query processor. These responsibilities are divided into several subcomponents, including:
File manager: The file manager is responsible for managing the physical storage of data on disk, including creating, deleting, and modifying files. It also handles operations such as allocating and deallocating disk space, and managing data blocks within files.
Buffer manager: The buffer manager is responsible for managing the buffer pool, which is a portion of main memory used to store frequently accessed data. It handles operations such as reading data from disk into the buffer pool, and writing data from the buffer pool back to disk.
Access methods: Access methods are algorithms for reading and writing data to and from disk. They include methods such as sequential access, random access, and indexing.
Data dictionary: The data dictionary is a metadata repository that stores information about the structure of the database, including data types, relationships between tables, and access permissions. The storage manager uses the data dictionary to translate high-level data requests from the query processor into low-level file system operations.
The storage manager is responsible for ensuring that data is stored efficiently and securely on disk, and that it can be accessed quickly and accurately by the query processor. It plays a critical role in the overall performance and reliability of the database system, and is a key factor in determining the scalability and responsiveness of the system.
