Acronis Access Server uses PostgreSQL as it's database storage.
Documentation on the latest PostgreSQL (for other versions visit this site).
List of error codes.
When installing Acronis Access server, by default you also install pgAdmin. It provides a graphical user interface to PostgreSQL. For documentation on all versions of pgAdmin visit this site.
Useful information can be found at the PostgreSQL Wiki, including a troubleshooting guide.
For anti-virus related problems check this article.
For information on backing up a PostgreSQL database: PostgreSQL backup.