I have  found  the file: 05.04.00.log.resorces in Providers/DataProviders/SqlDataProvider  and caontains this:

System.Data.SqlClient.SqlException: The ALTER TABLE statement conflicted with the FOREIGN KEY constraint "FK_PortalLocalization_Portals". The conflict occurred in database "dnn_lampo", table "dbo.Portals", column 'PortalID'.
   at System.Data.SqlClient.SqlConnection. (SqlException exception, Boolean breakConnection)
   at System.Data.SqlClient.TdsParser.ThrowExceptionAndWarning(TdsParserStateObject stateObj)
   at System.Data.SqlClient.TdsParser.Run(RunBehavior runBehavior, SqlCommand cmdHandler, SqlDataReader dataStream, BulkCopySimpleResultSet bulkCopyHandler, TdsParserStateObject stateObj)
   at System.Data.SqlClient.SqlCommand.RunExecuteNonQueryTds(String methodName, Boolean async)
   at System.Data.SqlClient.SqlCommand.InternalExecuteNonQuery(DbAsyncResult result, String methodName, Boolean sendToPipe)
   at System.Data.SqlClient.SqlCommand.ExecuteNonQuery()
   at DotNetNuke.Data.SqlDataProvider.ExecuteADOScript(String SQL)
   at DotNetNuke.Data.SqlDataProvider.ExecuteScript(String Script, Boolean UseTransactions)



/* Add Foreign Key to PortalLocalization Table */
/***********************************************/

IF NOT EXISTS (SELECT * FROM dbo.sysobjects WHERE id = object_id(N'FK_PortalLocalization_Portals') AND OBJECTPROPERTY(id, N'IsForeignKey') = 1)
    BEGIN
        /* add key and cascade delete rule */
        ALTER TABLE dbo.PortalLocalization
            ADD CONSTRAINT FK_PortalLocalization_Portals
                FOREIGN KEY ( PortalID ) REFERENCES dbo.Portals ( PortalID ) ON DELETE  CASCADE
    END   

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What does it mean?

Thanks