The objectQualifier is an optional parameter of the SqlDataProvider
The objectQualifier attribute is used to control the prefix applied to every object in the SQL Server database. By default this is set to an empty string “”, so for instance the “Portals” table is created as “Portals”. If, for example, the objectQualifier was set to “dnn_” then the “Portals” table would be created as “dnn_Portals” and stored procedures etc that referenced the Portals table wold reference it as dnn_Portals. Setting this value is recommended, as it allows DotNetNuke to exist within an environment where multiple applications might need to use the same database.
In the case of Upgrades it is important to confirm that this value is consistent with the existent installation ie. once DotNetNuke is installed the objectqualifier cannot be changed.