In a distributed database, data is stored in different systems across a network. For Example, in mainframes, personal computers, laptops, cell phones, etc.
Advantages of distributed database:
1) In a distributed database, data can be stored in different systems like personal computers, servers, mainframes, etc.
2) A user doesn’t know where the data is located physically. Database presents the data to the user as if it were located locally.
3) Database can be accessed over different networks.
4) Data can be joined and updated from different tables which are located on different machines.
5) Even if a system fails the integrity of the distributed database is maintained.
6) A distributed database is secure.
Disadvantages of distributed database:
1) Since the data is accessed from a remote system, performance is reduced.
2) Static SQL cannot be used.
3) Network traffic is increased in a distributed database.
4) Database optimization is difficult in a distributed database.
5) Different data formats are used in different systems.
6) Different DBMS products are used in different systems which increases in complexity of the system.
7) Managing system catalog is a difficult task.
8) While recovering a failed system, the DBMS has to make sure that the recovered system is consistent with other systems.
9) Managing distributed deadlock is a difficult task.