Several criteria are normally used to classify DBMSs.

1. The first is the data model on which the DBMS is based. We can categorize DBMSs based on the data model: relational, object, object-relational, hierarchical, network, and other.

 

1. The second criterion used to classify DBMSs is the number of users supported by the system.

• Single-user systems support only one user at a time and are mostly used with personal computers.
• Multiuser systems, which include the majority of DBMSs, support multiple users concurrently.

 

1. A third criterion is the number of sites over which the database is distributed. A DBMS is centralized if the data is stored at a single computer site.

 

1. A centralized DBMS can support multiple users, but the DBMS and the

              database themselves reside totally at a single computer site.

1. A distributed DBMS (DDBMS) can have the actual database and DBMS  

               software distributed over many sites, connected by a computer network.

1. Homogeneous DDBMSs use the same DBMS software at multiple sites