PowerServer Performance Tuning Guide
Technique #2: thin-out “heavy” UI logic

Use batch operations instead of performing a single operation many times. For example, the execution of the following "batch" code is two to three times faster than the original code.

For I = 1 To 100
	dw_1.SetItem(ll_i,+
                           "name",+
                           dw_2.GetItemString(ll_i,"name"))
                      ...
Next

dw_1.RowsCopy(1,100,Primary!,dw_2,1,100,Primary!)