A B-Tree used as an index for a large database table has four levels including the root node. If a new key is inserted in this index, then the maximum number of nodes that could be newly created in the process are

The maximum number of nodes that could be newly created when a new key is inserted into a B-Tree index with four levels including the root node depends on the order of the B-Tree.

Here are the steps to calculate it:

1. Identify the order of the B-Tree. The order of a B-Tree is the maximum number of children each node can have. Let's assume the order is 'm'.

2. When a new key is inserted, the worst-case scenario is that all nodes are full and need to be split. A node split happens when a node is full and a new key is inserted into it. The node is split into two nodes and the middle key is moved up to the parent node.

3. In a B-Tree of four levels, the maximum number of nodes that could be newly created when a new key is inserted would be 4. This is because a new key insertion could cause a split at the leaf level, which could cause a split at the level above, and so on up to the root.

4. Therefore, in the worst-case scenario, a new key insertion could cause the creation of a new node at each level of the B-Tree. Since there are four levels in the B-Tree, the maximum number of nodes that could be newly created is 4.

Please note that this is a simplified explanation and the actual number could be less depending on the state of the B-Tree at the time of insertion.