About Denbun system
Denbun saves any data in the database.
Therefore, it simply separates cgi programs and data.
However the cgi programs use OS file system for temporary files.

Backup and restore data
Since Denbun saves any data in the database, you can backup "dnpwmldb". (exception (*1))
To backup data, you can use pg_dump command or other standard way provided by PostgreSQL.
Please refer the PostgreSQL documentation.

*1 Users' photos registered by the administrators are not stored in the database. If you wish to backup the data, backup the directory "dnpwml/dnpwmlfile".

e.g.
pg_dump -b -Fc -U postgres dnpwmldb > dnpwmldb.pgdmp

To restore the data, you can use pg_restore command or other standard way provided by PostgreSQL.
Please refer the PostgreSQL documentation.

e.g.
dropdb -U postgres dnpwmldb
pg_restore -C -Fc -U postgres -d template1 ./dnwmldb.pgdmp

However if you use other backup tool, please follow the way provided by the tool.