<div class="content"><p>The _PERF_INSTANCE_HEADER structure is used at the beginning
of an instance block that is returned when enumerating <a href="da82a046-4e10-46ab-8da9-3d24bb48a2b2#gt_5ad9937c-a24e-4274-92c8-50ff5f97bf19" data-linktype="relative-path">counterset</a> instances or
when returning <a href="da82a046-4e10-46ab-8da9-3d24bb48a2b2#gt_35645a67-9e0b-4c05-b2d9-3b2b25f2beac" data-linktype="relative-path">performance
counter</a> data from multiple instances.</p><dl>
<dd>
<div><pre> typedef struct _PERF_INSTANCE_HEADER {
   unsigned long Size;
   unsigned long InstanceId;
 } PERF_INSTANCE_HEADER,
  *PPERF_INSTANCE_HEADER;
</pre></div>
</dd></dl><p><b>Size:</b>  The total size, in bytes, of the
structure and the instance name.</p><p><b>InstanceId:</b>  The counterset instance
identifier. Each active instance of a counterset can be identified by the
combination of its instance name and instance identifier. Two active instances
of a counterset SHOULD NOT have the same combination of instance name and
instance identifier. <a id="Appendix_A_Target_3"></a><a aria-label="Product behavior note 3" href="74af7798-f739-49d0-b16f-6899a9f92a8a#Appendix_A_3" data-linktype="relative-path">&lt;3&gt;</a></p></div>