The Session.rebalance method can be used to rebalance data sources' underlying btrees. If a tree has become unbalanced (that is, one part of the tree is excessively deep), Session.rebalance rewrites the tree as a balanced tree.
The data source must be quiescent.
The Session.rebalance method should never be needed, as WiredTiger btrees are maintained as balanced trees. It is only provided as a tool to handle the unexpected.