This section reports index maintenance activity caused by page splits in allpages-locked tables with clustered indexes. These splits require updating the nonclustered indexes for all of the rows that move to the new data page.
“RID Upd from Clust Split” reports the total number of page splits that required maintenance of a nonclustered index.
“# of NC Ndx Maint” reports the number of nonclustered rows that required maintenance as a result of row ID update operations.
“Avg NC Ndx Maint/Op” reports the average number of nonclustered indexes entries that were updated for each page split.