OpenMeetings default configuration is to use H2.
It is recommended for production environments and high availibility to change to an usual relational database like Oracle, MySQL, Postgres, MSSQL or DB2.
For more information about H2 see https://www.h2database.com
There is a sample configuration for H2 that ships with every release in:
If you encounter issues, you can drop the db and then run the web based installer again