What is the primary advantage of using a B*-tree over a B-tree for indexing data?

The primary advantage of using a B*-tree over a B-tree for indexing data lies in the way B*-trees handle space utilization.

1. Space Utilization: B*-trees guarantee that each internal node (except for the root) is at least 2/3 full instead of half full, as in the case of B-trees. This means that B*-trees make better use of space and require fewer disk accesses.

2. Redistribution: When an insertion into a B*-tree causes a node to overflow, the B*-tree redistributes keys among the node and its siblings before splitting the node. This redistribution delays the splitting of nodes and leads to B*-trees having fewer nodes (and therefore fewer disk accesses) than equivalent B-trees.

3. Insertion and Deletion: The redistribution of keys also makes the insertion and deletion operations more efficient in B*-trees compared to B-trees.

In summary, the primary advantage of B*-trees over B-trees is their better space utilization and efficiency in terms of disk access, which is a critical factor in database systems where disk access time is a significant bottleneck.