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How the NetWare Peripheral Architecture Works

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John Mauzy
Novell, Inc.

18 Oct 2000

The NetWare Peripheral Architecture (NWPA) is the interface between mass storage drivers and the NetWare operating system. The NWPA.NLM module is embedded within the SERVER.EXE file. When SERVER.EXE executes, it automatically loads NWPA.NLM.

After the HAM (Host Adapter Module) drivers are loaded for each of the adapters, NWPA.NLM commands the HAMs to scan their buses for devices. It then loads the appropriate Novell CDM (Cxxx Dxxx Mxxx) drivers for the device types that the HAM drivers were able to find.

You can load a different NWPA.NLM than the one embedded in SERVER.EXE by putting the desired NWPA.NLM file in the NetWare boot directory (the directory where the SERVER.EXE file resides). NetWare looks in the boot directory for an alternate NWPA.NLM before it loads the embedded one.

After NWPA.NLM is loaded, you can unload it like any other .NLM file by using the unload command (for example, you can type UNLOAD NWPA <Enter> at the server console prompt). However, to do this you must first unload all of the HAMs and CDMs, because they are dependent on the NWPA.NLM. Once the CDMs and HAMs are unloaded and the NWPA.NLM unloads, all of the devices are deactivated.

If you unload NWPA.NLM, you can load the NWPA.NLM that is embedded in SERVER.EXE by typing LOAD *NWPA <Enter> at the server prompt. To load an alternate NWPA.NLM, you must also specify the directory path (for example, LOAD C:\NWSERVER\NWPA <Enter>).

The NWPA.NLM has two load options that not many know about. These are:

  • NWPA /naload <Enter>. The No Auto Load option prevents NWPA.NLM from automatically loading the Novell CDM drivers.

  • NWPA /nascan <Enter>. The No Auto Scan option prevents NWPA.NLM from commanding the HAM drivers to scan their buses.

To use these options you must unload NWPA.NLM first, because NetWare will automatically load the NLM without options when the SERVER.EXE executes.

* Originally published in Novell AppNotes


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