typedef struct _STACK_TRACE_DATABASE
{
     union
     {
          CHAR Resource[56];
          PVOID Lock;
     };
     VOID * Reserved[3];
     UCHAR PreCommitted;
     UCHAR DumpInProgress;
     PVOID CommitBase;
     PVOID CurrentLowerCommitLimit;
     PVOID CurrentUpperCommitLimit;
     CHAR * NextFreeLowerMemory;
     CHAR * NextFreeUpperMemory;
     ULONG NumberOfEntriesLookedUp;
     ULONG NumberOfEntriesAdded;
     PRTL_STACK_TRACE_ENTRY * EntryIndexArray;
     ULONG NumberOfEntriesDeleted;
     ULONG NumberOfEntriesAvailable;
     ULONG NumberOfEntriesReused;
     ULONG NumberOfAllocationFailures;
     PRTL_STACK_TRACE_ENTRY FreeLists[32];
     ULONG NumberOfBuckets;
     PRTL_STACK_TRACE_ENTRY Buckets[1];
} STACK_TRACE_DATABASE, *PSTACK_TRACE_DATABASE;

Windows Vista Kernel Structures