链接数据库时，几个可以设置timeout的地方
1.Configuring (Server Configuration Options - remote query timeout )( but Not Recommended)
The remote query timeout option specifies how long, in seconds, a remote operation can take before SQL Server times out. The default value for this option is 600, which allows a 10-minute wait. This value applies to an outgoing connection initiated by the Database Engine as a remote query. This value has no effect on queries received by the Database Engine. To disable the time-out, set the value to 0. A query will wait until it is canceled.
For more information see below Urls,
http://technet.microsoft.com/en-us/library/ms189040.aspx
http://technet.microsoft.com/en-us/library/ms189631.aspx
这里需要注意的是，remote query timeout只针对linked server有效。下面对remote query timeout的解释中说明了，remote query timeout通过设置 SQL Server Native Client OLE DB provider rowset properties中的DBPROP_COMMANDTIMEOUT起效，而 SQL Server Native Client OLE DB provider的作用就是“By using the SQL Server Native Client OLE DB Provider, SQL Server distributed queries can query data in remote instances of SQL Server.”。
http://technet.microsoft.com/en-us/library/ms177457(v=sql.105).aspx
因此，对于SQL server database engine而言，是没有timeout这个概念的，query会一直运行下去，除非客户端cancel。而也只有client端可以限制timeout。remote query timeout的作用原理是provider的超时的概念，一旦超时，provider便cancel query。
下面的方法也是通过在链接字符串中规定timeout。
2.In web config connection string you can specify Connection Timeout argument .(This setting for the entire application who access this connection
| Connect Timeout -or- Connection Timeout |
The length of time (in seconds) to wait for a connection to the server before terminating the attempt and generating an error. |
For more information see below URL
http://www.connectionstrings.com/articles/show/all-sql-server-connection-string-keywords
3.You can change the command time out property for particilar command. in front end coding.(This is for particular command or depends on architecture design of the application)
http://msdn.microsoft.com/en-us/library/system.data.sqlclient.sqlcommand.commandtimeout(v=VS.100).aspx
4. 对于SQL Server backup而言，也是会timeout的。
If a backup operation overlaps with a file-management or shrink operation, a conflict arises. Regardless of which of the conflicting operation began first, the second operation waits for the lock set by the first operation to time out (the time-out period is controlled by a session timeout setting). If the lock is released during the time-out period, the second operation continues. If the lock times out, the second operation fails.