Keeping data in one place so that all applications can access it may work just fine if the data load is not high. When the number of applications increases, it would be a natural decision to separate them in such a way that they don't access the data source simultaneously.

One of the solutions is to create an exact copy of the data source, a replica. The process of creating a replica is called replication.

Consider, for example, a database that is constantly being updated. It could be a financial database with information about customer accounts and transactions. It could be an inventory database that reflects the status of merchandise in several stores. Every hour the organizations need to perform analysis to understand the trends, they need to run reports, or to perform other tasks on data, which could be quite resource-consuming. If these operations are performed on the live database, they may interrupt regular access to the database by other applications...