This activity is used to unfreeze a frozen sub contract revision. In some cases, it may be necessary to modify a sub contract revision after it has been frozen. However, note that this process is not recommended. When you unfreeze a sub contract revision and then modify it, the ability to compare baselines and track changes on the revision will be lost.
Once the revision is unfrozen, you can perform changes on the contract lines and items, where the changes will be logged in the Change History tab.