unit 5 DMS notes

https://drive.google.com/file/d/1Aw3IRj-FRUGASVZF05HfVc35ortuzAUf/view?usp=sharing

This document covers fundamental concepts in Database Management Systems (DBMS), focusing on how data is stored on external memory and methods for efficient data retrieval. Since primary memory is volatile and limited, external storage devices like disks are used for permanent data storage. The file organization defines how records are mapped onto disk blocks, with different types including Heap, Sequential, Hash, and Clustered. To speed up searching in files, especially those with unsorted records, indexing is used. An index is a smaller table with key-value pairs pointing to the disk block addresses of records. Various indexing techniques are discussed, such as Primary, Secondary, Clustering, and Hash-Based indexing, including Static and Dynamic Hashing (Extendable and Linear Hashing). The document also introduces tree-based indexing structures like Indexed Sequential Access Methods (ISAM) and B+ Trees, which are crucial for efficient insertion, deletion, and search operations.

Here are 5 key topics covered:

• File Organization: Defines the method by which file records are mapped onto disk blocks, determining how data is physically structured and stored.
• Indexing: A data structure technique used to quickly retrieve records from a database file, often consisting of a small table mapping key values to disk block addresses.
• Primary Indexing: An index created using the primary key of a table, offering efficient searching as primary keys are unique and stored in a sorted manner. It can be classified as dense or sparse.
• Static Hashing: A hashing method where the hash function produces only a fixed number of hash values, mapping search-key values to a fixed set of bucket addresses. Collision resolution techniques like Open Addressing (Linear, Quadratic, Double Probing) and Separate Chaining are used.
• B+ Trees: A dynamic index structure that is an extension of a Binary Tree, allowing for efficient insertion, deletion, and search operations, where data is stored only in the leaf nodes.