(Adam)Distribution transparency is the database management software feature that makes a distributed database look like a single database to users (Coronel & Morris, 2019). Since distributed databases can be spread all over the network of a connected system, a distribution transparency can make it look like that isn’t the case to whoever is looking at it. Transparency is provided at three different levels: fragmentation transparency, location transparency, and local mapping transparency.
Fragmentation transparency is the idea that your database will work without fragment names or locations. While the DB is fragmented, it works just like a database that is stored at a centralized location with a single name. This is a benefit to the users because the DDB would just work for them. They don’t need to know the name and how to navigate to the appropriate directory to get to the database. It would look just like the traditional centrally managed DB’s they are used to seeing.
The next level down is location transparency which is the idea that you do have to specify the database fragments name, but you do not need to specify where those pieces are located. You can see why this is a step lower since it requires information that fragmentation transparency didn’t. This still provides some benefits to organizations, but not as much as the previous level. Employees are going to need to remember the names of the fragments and that shouldn’t be too difficult.
Finally, local mapping transparency is when the users need to know both the name and location of the DB fragments. A distributed database that is operating at the local mapping transparency has a very low or no level of distribution transparency. This is obviously the least optimal level for the users. In this case everyone needs to know where the specific fragments are stored and which one in which location is the one they need. This could cause a lot of confusion because navigating to the wrong directory could lead to extensive search times and possible issues if they remember only half of the equation.
Reference:
Coronel, C., & Morris, S. (2018). Database Principles: Fundamentals of Design, Implementation, and Management. Cengage.
