Sakar Pradhananga

Four Layers of Distributed Query Processing Distributed Query Processing in a Distributed Database System (DDBMS) involves the process of executing a query across multiple databases or sites in a distributed environment. The process of query execution is broken down into four layers: Query Decomposition Process Query decomposition is a critical step in distributed query processing. … Read more

Updatable and Non-updatable Views Updatable View: An updatable view is a view in a database that allows users to perform insert, update, and delete operations on the underlying tables through the view itself. This means that any changes made to the view are reflected in the base tables that the view is built upon, as … Read more

A-D-H Architecture of Distributed Database (DDB) The A-D-H architecture is a design model used for distributed databases, consisting of three layers that organize the system’s components and their functions. Here’s a breakdown of each layer: Why Fragmentation is Important in Distributed Databases? Fragmentation is the process of dividing a database into smaller, manageable pieces called … Read more

Three Orthogonal Dimensions of Distributed Database Design When designing a distributed database system, there are three main orthogonal dimensions to consider. These dimensions refer to different aspects of the database design that are important for creating an efficient, reliable, and scalable distributed system. 1. Data Distribution: Data Distribution refers to how the data is divided … Read more

Distributed Database System (DDBS) A Distributed Database System (DDBS) is a database system where the data is stored across multiple physical locations (sites), but it works as a single unified system. These sites are connected via a network, and users interact with the system as though it’s one database, even though the data is distributed. … Read more

Timestamp-based concurrency control is a mechanism used to manage concurrent access to the database while ensuring serializability (the highest level of isolation in transactions). It is an alternative to other methods like locking-based concurrency control, and it relies on assigning each transaction a unique timestamp to determine the order of execution. This method ensures that … Read more

The INGRES algorithm refers to the method developed for query optimization and execution in the INGRES Database Management System (DBMS). INGRES, which stands for Interactive Graphics and Retrieval System, was an early relational DBMS developed at the University of California, Berkeley, in the 1970s and 1980s. It introduced several innovations that later influenced the design … Read more

A parallel database is a type of database system that uses parallel processing to improve performance, particularly for large-scale data processing and querying tasks. Parallelism in a database refers to the ability to execute multiple operations simultaneously, which allows the database to handle large amounts of data more efficiently and reduce the time it takes … Read more

Importance of Log Records in Recovery In database systems, log records are crucial for recovering the database to a consistent state after a failure, like a system crash. Log records store the details of what changes were made by each transaction. These records are used to: 2-Phase Commit (2PC) Protocol The 2-Phase Commit (2PC) protocol … Read more

Properties of a Transaction (ACID Properties) In database management systems (DBMS), a transaction is a sequence of one or more operations (such as insert, update, delete, or read) that are executed as a single unit. The ACID properties ensure the correctness and reliability of the transaction, particularly in the case of failures or concurrent access. … Read more