Batch Updating List WSS 3.0

In Windows SharePoint Services 3.0, sometimes you must update multiple items in a list. Creating a foreach loop to iterate through a list item collection and performing an Update on each list item can be very intensive. An alternative approach is to construct a Collaborative Application Markup Language (CAML) string that contains a batch of commands to perform the updates and execute the commands by using the ProcessBatchData command of an SPWeb object. This Microsoft Office Visual How To demonstrates how to construct and execute a batch of commands to update text and date fields for all items in a list.

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Exemplo: http://the-simple-programmer.blogspot.com/2011/01/sharepoint-2007-batch-update-example.html
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(fonte: http://msdn.microsoft.com/en-us/library/cc404818(v=office.12).aspx)