It’s recommented to use the MySQL backend for production use. I used SQLlite for my tests, because it was easier. When I wanted to go productive, I used the migration guide but found that the MySQL user / password could not be read from command line. I had to enter the MySQL root password in order to complete the migration.

For reference the commands I created DB and user with:

CREATE USER 'opendnssec'@'localhost' IDENTIFIED BY 'SECRET';
GRANT ALL PRIVILEGES ON opendnssec.* TO 'opendnssec'@'localhost' IDENTIFIED BY 'SECRET';

Then the migration step:

root@a:~/opendnssec/opendnssec-1.4.3# enforcer/utils/convert_database.pl --from dbi:SQLite:dbname=/var/lib/opendnssec/kasp.db --to dbi:mysql:database=opendnssec;host=localhost
Connected to exporting database dbi:SQLite:dbname=/var/lib/opendnssec/kasp.db
Validating existing data
Create the importing database, this will delete existing data? [NO/yes] yes
Enter importing database password (--to-password): ROOTMYSQLPASSWORD
Connected to importing database dbi:mysql:database=opendnssec;mysql_multi_statements=1
Initializing conversion
Deleting existing data in importing database
Converting database
        securitymodules
        categories
        parameters
        serialmodes
        policies
        zones
        keypairs
        dnsseckeys
        parameters_policies
Optimizing database
Done

It seems that the Debian package does not contain the migrate script, I used the one from source tarball.