Connect to metabase h2 database via H2 Shell

Background: The h2 database of my metabase release suddenly jumped form ~200Mb to 1.7GB:

  198M	metabase.db.h2.db_2016-11-09-02-30.bz2
  1.7G	metabase.db.h2.db_2016-11-10-02-30.bz2

Of course, Metabase just refuses to connect to the database (timing out).

So now I am trying to troubleshoot this, and to do that I am attempting to connect to the big h2 database using the h2 shell. However, It keeps telling me that the password is wrong:

ubuntu@mydomain:/tmp$ java -cp h2*.jar org.h2.tools.Shell
Welcome to H2 Shell 1.4.193 (2016-10-31)
Exit with Ctrl+C
[Enter]   jdbc:h2:~/test
URL       jdbc:h2:./metabase.db.h2.db
[Enter]   org.h2.Driver
Driver
[Enter]
User
[Enter]   Hide
Password
Password
SQL Exception: Wrong user name or password [28000-193]
[Enter]   jdbc:h2:~/test
URL

I am not setting any user or password when trying to read the DB, (I press ENTER when prompted for a password).

Does anyone know either

  1. What should I set in Username and Password
  2. Why did my DB size suddenly increased that much?