To use H2 as storage in OntoBroker, you have to set at least two values in your OntoConfig.prp:
Storage = H2
H2.URL = jdbc:h2:file:<path>/<dbname>
The path can be omitted or can be relative to the working directory. As a folder separator you should use the normal slash / instead of the backslash \.
H2.URL = jdbc:h2:file:data/edb
This will create the database files in the subdirectory data (relative to the working directory) and all database files will start with "edb".
H2.URL = jdbc:h2:file:d:/home/storage/mydb
This will create the storage files in the directory d:\home\storage and all storage files will start with "mydb".
H2 may create, enlarge and delete files all the time, even if you are using OntoBroker with reading access only. Therefore OntoBroker with H2 needs create and write permissions on the directory where the storage files are located.