Not explicitly clear what it does do. In principle, it should be reviewing all "share change" transactions -- Buys, Sells, Add, Remove, Reinv___, and possibly RtrnCap. The Sells and Removes should be cross-checking versus lot specifications for those transactions - that no lot has been committed to a sale more than once. It cannot be restricted to a single account. It should not 'damage' an account in good working order. It is often considered to be good policy to have a backup before any Validate and Repair function is applied.