The _PERF_DATA_HEADER structure is used at the beginning of a sequence of counter header blocks that are returned when the client queries the server for performance counter values.

 typedef struct _PERF_DATA_HEADER {
   unsigned long dwTotalSize;
   unsigned long dwNumCounter;
   unsigned __int64 PerfTimeStamp;
   unsigned __int64 PerfTime100NSec;
   unsigned __int64 PerfFreq;
   SYSTEMTIME SystemTime;

dwTotalSize: The total size, in bytes, of the data.

dwNumCounter: The number of counters whose value is retrieved.

PerfTimeStamp: A high-resolution clock.

PerfTime100NSec: The number of 100 nanosecond intervals since January 1, 1601, in Coordinated Universal Time (UTC).

PerfFreq: The frequency of a high-resolution clock.

SystemTime: The time at which data is collected on the provider side. The format of this field is as specified in [MS-DTYP].