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Check in for the same change set created for submitting review in RTC 6.0.6

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Once a change set is completed/closed, further file changes cannot be added to that change set. This is by design.
This also ensures that what is under code review does not suddenly change for the reviewer, and also ensures the code that was reviewed (and approved for example) will not change after the fact.
The recommended approach is to check-in further changes into a different change set, and associate that change set to the work item and re-submit the work item for code review. The different change sets also help capture what actually happened, such as what was actually changed for that review cycle, and other metadata such as a new change set comment, and change set completion date, etc.