SharePoint Batch Insert/Update/Delete Performance

When you want to do bulk transaction insert, update, or delete.
If you have to update a larger number of items its highly recommended to not use the Update method on every item. Instead – use the batch update function ProcessBatchData provided by SPWeb.

StringBuilder query = new StringBuilder(); for (int itemIx=0;itemIx<100;itemIx++) {   query.AppendFormat("" +           "{1}" +           "New" +           "Save" +           "{2}" +        "", i, listGuid, someValue, "urn:schemas-microsoft-com:office:office#"); } SPContext.Current.Web.ProcessBatchData("" +     "{0}", query.ToString())

For more details of using ProcessBatchData check url:
http://stefan-stanev-sharepoint-blog.blogspot.com/2009/07/tips-for-using-spwebprocessbatchdata.html