What is a parallel database and explain how it works?

History of Parallel Execution

The activity in parallel computing dates returned to the late 1950s, with developments emerging in the form of supercomputers during the ‘60’s and ‘70’s. These have been shared-memory multiprocessors, with more than one processor working side-by-side on shared information.
In the mid-1980s, a new form of parallel computing was released when the Caltech Concurrent Computation project develop a supercomputer for scientific purposes from 64 Intel 8086/8087 processors.
In today, parallel computing is turning into mainstream depends on multi-core processors. Most desktop and laptop systems now dispatch with dual-core microprocessors, with quad-core processors freely accessible. Chip manufacturers have started to improve complete processing implementation by adding extra CPU cores.

What is the difference between Concurrency and Parallel Execution in Computer Architecture?

Concurrency Execution

It is the sensual behavior of the N-Client I-Server model where one client is served at any provided moment. This model has dual characteristics. It is sequential on a small time scale, but together on a rather large time scale.

In this method, the elementary problem is how the competing clients, processors or threads, must be scheduled for service (Execution) through the single-level (processor). Scheduling policies can be oriented toward efficient service in terms of highest throughput (least intervention) or towards short average response time, and so on.
The scheduling policy can be considered as covering two methods as first deals with whether servicing a client can be stopped or not and therefore, on what occasions (pre-emption rule). The other states how one of the competing clients is choosing for services (selection-rule) as displayed in the figure.

If pre-emption is not enabled, a client is serviced for considering required. This gives results in slightly longer waiting times or the blocking of essential service requests from various clients. The pre-emption rule can determine time-sharing, which confines continuous service for each client to the continuation of a time slice, or can be priority-based, interrupting the functions of a client when a higher priority client request services.
The selection rule depends on specific parameters, including priority, time of arrival, etc. This rule defines an algorithm to specify a numeric value, which we will declare the rank, from the given parameter.