并行数据库和分布式数据库的区别

1.并行数据库：
并行 DBMS 是一种跨多个处理器运行的 DBMS，旨在尽可能并行执行操作。并行 DBMS 链接许多较小的机器，以实现与单个大型机器相同的吞吐量。

特征 ：

1. CPU并行工作
2. 它提高了性能
3. 它将大型任务划分为各种其他任务
4. 完成工作非常快

2.分布式数据库：
分布式数据库被定义为在不同站点上的计算机网络上物理分布的共享数据的逻辑相关集合。分布式数据库管理系统被定义为允许管理分布式数据库并使分布式数据可供用户使用的软件。

特征 ：

1. 它是一组逻辑相关的共享数据
2. 数据被分成不同的片段
3. 可能存在片段的复制
4. 这些站点通过通信网络连接

并行数据库和分布式数据库的主要区别在于前者是紧耦合，然后是松耦合。

并行数据库和分布式数据库的区别：

Parallel Database	Distributed Database
In parallel databases, processes are tightly coupled and constitutes a single database system  i.e., the parallel database is a centralized database and data reside in a single location	In distributed databases, the sites are loosely coupled and share no physical components i.e., distributed database is our geographically departed, and data are distributed at several locations.
In parallel databases, query processing and transaction is complicated.	In distributed databases, query processing and transaction is more complicated in distributed database systems
In parallel databases, it’s not applicable.	In distributed databases, a local and global transaction can be transformed into distributed database systems
In parallel databases, the data is partitioned among various disks so that it can be retrieved faster.	In distributed databases, each site preserve a local database system for faster processing due to the slow interconnection between sites
In parallel databases, there are 3 types of architecture: shared memory, shared disk, and shared shared-nothing.	Distributed databases are generally a kind of shared-nothing architecture
In parallel databases, query optimization is more complicated.	In distributed databases, query Optimisation techniques may be different at different sites and are easy to maintain
In parallel databases, data is generally not copied.	In distributed databases, data is replicated at any number of sides to improve the performance of systems
Parallel databases are generally homogeneous in nature	Distributed databases may be homogeneous or heterogeneous in nature.
Skew is the major issue with the increasing degree of parallelism in parallel databases.	Blocking due to site failure and transparency are the major issues in distributed databases.