It's jdbc only, with the main usage being in-memory.
Redis is considered an in memory store as well, even though it can persist it's data on disk too.
And the capability isn't what makes it in-memory either, as you can store a SQLite db only in-memory too, and nobody would consider it to be an in-memory database. You could technically do the same for PostgreSQL, though that's not officially supported and needs a little effort on the users part.
I guess my phrasing was poor if you misunderstood me there, but I do stand by what I said: while H2 is a great project in Java-Land, it's very different to what I understood the parents goal to be.
Redis is considered an in memory store as well, even though it can persist it's data on disk too. And the capability isn't what makes it in-memory either, as you can store a SQLite db only in-memory too, and nobody would consider it to be an in-memory database. You could technically do the same for PostgreSQL, though that's not officially supported and needs a little effort on the users part.
I guess my phrasing was poor if you misunderstood me there, but I do stand by what I said: while H2 is a great project in Java-Land, it's very different to what I understood the parents goal to be.