This article discusses COM functionality. COM Support was deprecated in Silk Performer 2011, so this information is only applicable up until Silk Performer version 2010 R2 . The special value "COM_NULL" is used in the function call ComSetInterface, it signals to the COM replay engine that it should pass a NULL value to the server instead of an interface pointer. This value is normally only used by the recorder when it captures a function call that passes an interface pointer to the COM server and that interface is not known to the recorder. This can happen if the interface is of a type unknown to the recorder, or if it has been created "outside" of the recorder spying on the client application. In most cases if you see this type of call in the recorded script, it is due to the client passing a callback interface to the server. Such a callback interface is actually a COM interface offered by the client (and not the server, as usual) and is used by the COM server for generating callbacks to the client. In such scenarios, the client can not easily be simulated by the SilkPerformer COM replay engine, as the simulated client (the replay engine) would need to offer the same callback interface as the real client. That is of course not the case by default. There are possible workarounds for that, but they require a lot of COM knowledge and scripting effort (in BDL and Visual Basic). The value "COM_NULL" must be used to set the value of a string parameter to the value "NULL" because the standard value "NULL" is not supported as an input parameter to the function ComSetString. NOTE: Since the introduction of GUI-level testing in SilkPerformer 2006 Release 2, it may be possible to loadtest applications that are not supported by SilkPerformer on the protocol- or API-levels by recording on the GUI level. Please refer to the GUI-Level Testing Support section of the Other Supported Environments chapter in the SilkPerformer User Guide for full details. Old KB# 19261
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