What are embedded databases?

About

embedded databases are database that run in an embedded mode:

It means that it:

• runs along the code of the application in the same thread
• does not run as a service (ie client server mode)

Pros/Cons

Pros:

• No need to install them
• Performance as they run in the same thread (For instance, the Java Derby Database will run in the same JVM as the application)
• Portable

Cons:

• No client/server mode (ie no external connection by default). By default, they are not bound to a socket. Some databases allow it but it needs extra effort.
• Without any service socket:
  • No sync without any extra software layer
  • Available only for the application, not for client.
  • only a single application can access a database at one time
  • no network access occurs.

List

• Sqlite (C with binding)
• Derby (Java, support also client/server, replication)
• H2 (Java)
• HSQLDb (Java)