csOc3NearEndPerfMonControl is a read-write enable/disable switch that, based on its name and the enable/disable syntax it shares with its far-end equivalent, turns near-end SONET/SDH performance monitoring on or off for this OC3 port (its source description was left blank). Since the numerous csOc3Section, csOc3Line, and csOc3Path current, interval, day, and previous-day error counters on this port depend on performance monitoring being active, disabling this switch would starve those counters of fresh data even though they'd keep reporting stale or zero values. For example, if an admin notices csOc3SectionCurrentESs and its siblings have stopped incrementing despite known line noise, checking that csOc3NearEndPerfMonControl is still set to enable is a reasonable first step.