Some applications are designed such that there is a limited number of threads which will access some shared resource, and others never will.
To access a resource in a protected way, one can simply suspend the other threads which represent a possibility of simultaneous update, and leave the remaining threads alone. This is therefore less intrusive than the critical section API's, but still may affect threads which do not represent a threat at this instant, due to other processing, timing, and so on.
DosSuspendThread API will cause a specific thread to no longer compete for the processor, until DosResumeThread is issued. A thread in this situation will have the status of 'frz'. It may not be possible, without an appropriate trace, to find out which thread suspended another.