Users nodeids are in the range
    Minimum: 1
    Maximum: 524288
The Min and Maximum are set in the Prefernces->Rman->User tab.
Custom nodes written in the c++ language such as patterns,
bxdfs and filters have corresponding "args" files. Each args
file must specify a unique "nodeid". Nodeids are registered
with Maya by the users custom "RenderMan_for_Maya.ini" file.
This report about c++ plugins is based on the following ini file:
Nodeid's assigned to the users args files:
17:       RfM_ris/Counter.args
17:       RfM_ris/CutrColorByRayHit.args
200:      RfM_ris/CutrColorByST.args
201:      RfM_ris/CutrBBones.args
202:      RfM_ris/CutrColorByHeight.args
3:        RfM_ris/CutrFaceColor.args
4:        RfM_ris/CutrPaperCup.args
5:        RfM_ris/CutrSideMask.args
6:        RfM_ris/CutrSparky.args
7:        RfM_ris/CutrVelvet.args
9:        RfM_ris/Stroboscopic.args
The nodeids for OSL shaders are assigned directly within the 
source code of the shader. Shaders do NOT have corresponding
args files.
Nodeid's assigned to the users OSL shaders:
10:        "RfM_osl/cutrSSSMaterials"
10:        "RfM_osl/menu_demo"
11:        "RfM_osl/id2color"
12:        "RfM_osl/TexturePickerCycle"
13:        "RfM_osl/TexturePickerNoise"
14:        "RfM_osl/AttributeTexname"
16:        "RfM_osl/UsePrimVar"
18:        "RfM_osl/ucf"
19:        "RfM_osl/attr2color"
2:         "RfM_osl/butterfly"
20:        "RfM_osl/attrToColor"
8:         "RfM_osl/lofty"
Errror: The following nodeids are being used more than once:
    10 : RfM_osl/menu_demo.oso
    10 : RfM_osl/cutrSSSMaterials.oso
    17 : Args/Counter.args.args
    17 : Args/CutrColorByRayHit.args.args
duplicate nodeids must be resolved manually.