If, during rebalancing, the Directory Server issues an alert that a subtree has been unavailable for too long, then you can use this tool to evaluate the problem.

For example, if the move-subtree tool is interrupted by a host machine going down unexpectedly, the subtree can't be successfully moved. You can use the subtree-accessibility tool to evaluate and correct any problems with the subtrees and then re-run the move-subtree tool.