It will limit the amount of memory the Domino Server/Notes Client does see. It actually even modifies the physical RAM reported in Notes statistics. All internal buffers are calculated on the basis of this new memory size and you have not to specify any extra parameter like the buffer pool size. There are a number of parameters you could tune and also parameters you cannot tune (internal automatic allocation). But PercentAvailSysResources will work for all of those buffers and is the recommended way of splitting resources. All the other parameters like the buffer pool sizes should only be changed if you really analyze memory allocation (e.g. read memory dumps and/or monitor buffer pool usage for an extended period of time).
You should use PercentAvailSysResources with a Citrix MetaFrame or Windows terminal server. For example, if there are 10 data directories on the terminal server, then the notes.ini in each client data directory could contain the parameter PercentAvailSysResources=10. This limits each user on the terminal server to only 10 percent of the server’s system memory. In an IBM Lotus Domino environment, the private and shared memory must reside in a limited virtual address space, which is usually 4 Gigabytes. Important: Make sure that the sum of the values you specify in each partition does not exceed 100 percent. To reserve system memory for other applications, you can choose values that total less than 100 percent.