A distributed database is a collection of information stored across multiple computers or physical locations, or perhaps spread over a network of interlinked computers.
In most cases, a distributed database is a bunch of smaller databases that keep the characteristics and structure of the primary system. Nonetheless, these smaller units run within their environment and on their software, hardware, and transaction load.
Since the database is divided into smaller local units, there are fewer queries and, hence, reduced latency, which also improves performance and dependability.
Distributed DBMS Architectures
There are three DDBS architecture modes, including:
- Peer – to – Peer
- Multi – DBMS
All these three architecture depends on the following:
- Distribution – How you want to distribute data to different sites.
- Autonomy – Dictates the nature of the database controls and the degree of independence of each database.
- Heterogeneity – Outlines the uniformity or variation of the small databases’ components, structure, and data models.
Types of distributed data
With the DDBs structure in mind, we can broadly classify distributed databases two main categories, homogeneous and heterogeneous. However, each category has further sub-divisions. In essence, we have four types of DDBs, as outlined below:
1. Homogeneous Distributed Databases
In a homogeneous distributed database system, the small databases are identical as they use the same DBMS or DBMS.
These small databases work together to process user requests, as though they are a single unit.
Also, they are accessible via a single interface, just like a single database.
Even so, there are two types of homogeneous DDBS, namely:
- Autonomous − Each small database remains independent and functions on its own. However, they have a linking application that shares data updates.
- Non-autonomous – Has a central or master DBMS with homogeneous nodes that distribute data through to its smaller systems and coordinates data updates across the sites.
2. Heterogeneous Distributed Database
Databases that use different sites and have different operating systems and structures are heterogeneous. That means they use different schemas and software.
These systems consist of different DBMSs with structures such as relational, hierarchical, network, or in some cases, object-oriented.
With dissimilar schemas and software, query processing and transaction processing is complex and not as straightforward as homogenous systems
While there may be coordination among these distributed databases, there is a limit as some systems may not even be aware of the existence of another. So, they mostly don’t work on user requests together.
There are two types of heterogeneous distributed database systems, namely:
- Federated − Independent but have a front-end application that provides a single source of data to enable them to function as a single database system.
- Un-federated – These systems have a central coordinating module that provides data on demand.
Advantage of Distributed Database
Many organizations prefer distributed database over a centralized model for many reasons, some of which include:
- Reliability – Just like an investment, you don’t want to keep all your eggs in one basket. In case of failure that could lead to data loss, only a part of the database experiences a setback, which minimizes data loss.
- Security and better control – You control part of your database that’s accessible to specific employees. It doesn’t only make it manageable but also increases the overall internal and external protection.
- Cost-effective – In most cases, your employees only access what they need only, decreasing the bandwidth cost.
- Local access –a localized database ensures your activities don’t stop because of a problem with the server. Employees can access the data locally.
- Growth – Distributed database makes it highly scalable as you can easily create a node within the database to cater for a new line of business.
- Speed & resource efficiency – Since most searches and requests are localized, there’s reduced remote traffic, which makes the system faster and efficient.
- Responsibility & containment – Most problems are contained locally without affecting other branches of the business.
Who Needs a Distributed Database?
Not everyone or an organization needs a distributed database. In some cases, your data can fit in a single MySQL server with much ease. In that case, a distributed database may be suitable. But there’s no one-size-fits-all situation that singles out the need for a distributed database system. Here are some of the deciding factors:
- Need for more capacity
- Slow query performance
- Need for scaling solutions
A robust distributed database solves scalability tailbacks and makes you avoid manual sharding and other “quick fixes!”