sec -trees figure simple deletion from -tree the record with key value is removed from the tree of figure note that even though is also placeholder used to direct search in the parent nodethat value need not be removed from internal nodes even if no record in the tree has key value thusthe leftmost node at level one in this example retains the key with value after the record with key value has been removed from the second leaf node figure deletion from the -tree of figure via borrowing from sibling the key with value is deleted from the leftmost leafcausing the record with key value to shift to the leftmost leaf to take its place note that the parent must be updated to properly indicate the key range within the subtrees in this examplethe parent node has its leftmost key value changed to determine if they have spare record that can be used to fill the gap if sothen enough records are transferred from the sibling so that both nodes have about the same number of records this is done so as to delay as long as possible the next time when delete causes this node to underflow again this process might require that the parent node has its placeholder key value revised to reflect the true first key value in each node figure illustrates the process if neither sibling can lend record to the under-full node (call it )then must give its records to sibling and be removed from the tree there is certainly room to do thisbecause the sibling is at most half full (remember that it had no records to contribute to the current node)and has become less than half full because it is under-flowing this merge process combines two subtrees of the parentwhich might cause it to underflow in turn if the last two children of the root merge togetherthen the tree loses level figure illustrates the node-merge