You must supply a DLL with your gateway that reads performace data from the memory-mapped files created by each gateway instance and places it in the Windows NT Registry so that the Windows NT Performance Monitor can access it. This DLL services the memory-mapped files for all instances of the gateway.
A performance monitor DLL must open the memory mapped files when the Performance Monitor starts, collect performance data each time the Performance Monitor requests a sample, and close the memory-mapped files when the Performance Monitor stops. Performance monitor DLLs use a counter structure for transferring data into the Windows NT Registry.
Performance monitor DLLs must implement the following functions.
| Function | Purpose |
|---|---|
| OpenGatewayPerformanceData | Opens the memory mapped files, creates a connection to the Windows NT application event log, and passes a copy of the counter structure to the registry. |
| CollectGatewayPerformanceData | Updates the performance data in the registry with data from the memory mapped files. There are multiple memory-mapped files if there are multiple instances of a gateway. In that case, The DLL can merge them into one structure before passing it to the Performance Monitor. |
| CloseGatewayPerformanceData | Closes the memory mapped files, frees memory used by the counter structure, and disconnects from the application event log. |
For more information about Performance Monitor DLLs and creating these routines, see the Windows NT Server Device Driver Kit (DDK) and the code for the GWPERF sample performance monitor DLL.