Do you mean you need the database schema (with details of tables and data structures in it) ?
It's available from your OpsCenter GUI - go to "Report" -> "Create New Report" -> "SQL Query" , there is a link there to download "refer to the OpsCenter Database Schema Document". If you don't see that, you need a "OpsCenter Analytics" license key.
Watson is correct... you will need an analytics license to create custom sql reports.
However, if you have one... then I believe you maybe looking for the following table / tables
If you have any other questions, please let me know.