tailieunhanh - Hướng dẫn học Microsoft SQL Server 2008 part 155

Theo mặc định, các thiết lập MOLAP tinh khiết được chọn. Thiết lập này hoạt động tốt cho các ứng dụng kho dữ liệu truyền thống bởi vì các phân vùng có thể được xử lý bởi cùng một thủ tục mà tải trọng lớn đồng loạt các dữ liệu vào kho. Pure MOLAP cũng là một lựa chọn tuyệt vời cho các phân vùng dữ liệu lịch sử mà bổ sung và cập nhật không mong đợi. | PartX Business Intelligence By default the pure MOLAP setting is chosen. This setting works well for traditional data warehousing applications because the partitions can be processed by the same procedure that loads large batches of data into the warehouse. Pure MOLAP is also an excellent choice for historical partitions for which data additions and updates are not expected. However if a partition is built based on frequently changing source data . directly on OLTP tables then proactive caching can manage partition updates automatically. Proactive caching Proactive caching is used to describe the many ways in which Analysis Services can automatically update the contents of a cube based on a relational data source. It is controlled by the many options on the Storage Options dialog but these options are all controls on the same basic procedure Analysis Services is notified each time underlying data is updated it waits for a pause in the updates and then begins rebuilding the cache partition . If an update notification is received before the rebuild completes then the rebuild will be restarted. If the rebuild process takes longer than allowed then the cache reverts to ROLAP SQL Queries until the rebuild is complete. The options that control the rebuild process are located on the Storage Options General tab select the Enable Proactive Caching check box to enable updates Silence Interval Amount of quiet time since the last update notification before beginning the rebuild process. An appropriate setting depends on the table usage profile and should be long enough to identify when a batch of updates has completed. Silence Override Interval After this amount of time begin the rebuild even if no silence interval has been detected. Latency The amount of time from receipt of the first notification until queries revert to ROLAP. Essentially this guarantees that data returned by Analysis Services will never be more outdated than the specified amount of time. Of course this .