H2 vs. Oracle Database vs. Realm vs. V Programming Language Comparison Chart

Welcome to H2, the Java SQL database. In embedded mode, an application opens a database from within the same JVM using JDBC. This is the fastest and easiest connection mode. The disadvantage is that a database may only be open in one virtual machine (and class loader) at any time. As in all modes, both persistent and in-memory databases are supported. There is no limit on the number of database open concurrently, or on the number of open connections. The mixed mode is a combination of the embedded and the server mode. The first application that connects to a database does that in embedded mode, but also starts a server so that other applications (running in different processes or virtual machines) can concurrently access the same data. The local connections are as fast as if the database is used in just the embedded mode, while the remote connections are a bit slower.

​Realm is a mobile-first, open source object database designed to run directly inside phones, tablets, and wearables. It provides a simple, object-oriented data model that eliminates the need for an ORM, allowing developers to define models as regular classes in languages like Swift, Java, Kotlin, C#, JavaScript, Dart, and C++. Realm's architecture ensures high performance and low memory usage by employing a zero-copy design, lazy loading, and multi-version concurrency control (MVCC) for thread-safe operations. It's live objects and collections automatically update across threads, enabling reactive programming patterns. Realm supports relationships between objects via links and backlinks, facilitating complex data structures. Developers can utilize tools like Realm Studio to inspect and manipulate local Realm databases and integrate Realm into various platforms, including React Native, Flutter, Xamarin, and Node.js.