csDs3Ds1IntervalValidData is a read-only TruthValue flag that says whether the performance counters recorded in this particular 15-minute historical bucket of the DS1-channel performance table nested inside this DS3 (csDs3Ds1IntervalTable) are trustworthy or not. Admins need to check this flag before trusting the paired error counters for that interval, since a false value means the agent could not reliably collect data for that period (for example, because the interface only came online partway through it, or the agent was a proxy that lost contact). For example, before flagging a spike found in bucket 7 of the DS1-channel performance table nested inside this DS3 (csDs3Ds1IntervalTable) as a real fault, an engineer first confirms the matching csDs3Ds1IntervalValidData value is true, so a temporarily-unreachable agent doesn't get misread as a live error burst.