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Distributed partitioned views in SQL Server 7.0 were not updateable. On SQL Server 2000 Enterprise Edition and Developer Edition servers, data can be modified through a distributed partitioned view:

set xact_abort on update vInventoryDist set UserName = 'unknown' where UserName is null and Country = 'Canada'

I needed to set the Xact_Abort option because each such statement is treated as a distributed transaction. Therefore, Distributed Transaction Coordinator must be running on each server. The result will look like this:

(2 row(s) affected) Rows Executes StmtText ---- -------- -------------------------------------------------------0 1 update vInventoryDist set UserName = 'unknown' where Use 0 1 |--Sequence 0 1 |--Remote Query(SOURCE:((local)\CANADA), QUERY:(UPDAT 0 1 |--Filter(WHERE:(STARTUP EXPR(0))) 0 0 | |--Remote Query(SOURCE:((local)\USA), QUERY:(UP 0 1 |--Clustered Index Update(OBJECT:(Asset.dbo.Invent 0 1 |--Filter(WHERE:(STARTUP EXPR(0))) 0 0 |--Clustered Index Seek(OBJECT:(Asset.dbo.Inv

Note that SQL Server has again created dynamic filters, and only the appropriate queries will be executed, although they are all incorporated in the execution plan. Unfortunately, views and modification statements have to satisfy additional requirements to allow modifications in that manner. I will mention only the most interesting and most restrictive ones: Member tables on other servers must be referenced using four-part names, the OpenRowset function, or the OpenDataSource function. These functions must not use pass-through queries. Member tables must not have triggers and cascading deletes or updates defined. All columns of a member table must be included in the distributed partitioned view. The order of the columns must be identical.

The column definitions in all base tables must match (data type, scale, precision, collation). Ranges of partition key values in member tables must not overlap. There can be only one Check constraint on the partitioning column and it may use only these operators: BETWEEN, AND, OR, <, <=, >, >=, =. Tables cannot have identity values (otherwise, Insert statements will fail). Partitioning keys cannot have defaults, allow nulls, be computed columns, or be timestamp values. smallmoney and smalldatetime columns on remote tables are automatically converted to money and datetime. Since all data types must match, the local table must use money and datetime. To avoid confusion it is best not to use smallmoney and smalldatetime. It is sometimes possible to work around some of these rules you can create an Instead-of trigger to modify the member tables directly. Unfortunately, in that case, query optimizer might not be able to create an execution plan as good as the one that would be created for a view that follows all the rules.

Federated servers and distributed partitioned views are not a magic bullet that will solve all your problems. Note that distributed partitioned views are primarily designed to improve scalability of the system, not its performance. Although these two parameters might seem similar to you, there is a significant difference. Performance refers to the speed of execution of the system (or of individual transactions), while scalability refers to the ability to increase transactional load or the number of concurrent users without significant performance degradation. For example, if a metric describing system performance is 100 percent on a single server, adding another server might cause performance to fall to, for example, 50 percent. In this case, end users would notice improvements only after a third server is added (3 50 percent). But the advantage is that we now have a system with nearly linear scalability every additional server would increase performance by another 50 percent. Federated servers (like other distributed database systems) are also more difficult to manage. Even simple operations, such as backups and restores, become very complicated. Promotion of hot fixes or new code in a production environment requires significant manual intervention or development of specialized tools. It is very important to evaluate the pros and cons of this design before you start. A rule of thumb is that all other options should be explored and exhausted first, and