From your posts it looks like you are a very new user who wants to do something with livelink. If you really wanted to know the categoryid in a livelink system.
From the GUI if you are on the "General" tab if you switch to categories you will see the URL turn into something like this
/llisapi.dll?func=ll&objId=170176241&objAction=attrvaluesedit&version=2&nexturl=%2Fllisapi%2Edll%3Ffunc%3Dll%26objid%3D164363628%26objAction%3Dbrowse%26sort%3Dname
Just for kicks I will explain what those are and how that can be read.
It is saying for the node identified by 170176241 edit the attributes for version 2 of the object and return me to where I came from(the next url)
when it does that an internal operation knows the category dataid and its version attached to it.
If you do a View Source and find the Category Name displayed there and look at the javascript function doSelectSchema you will see the category id that is defaulted or applied to the node.
Those are very inefficient ways what you should do and you ahve is.
1)get the NODE it is a very simple SOAP call.
2)Look for the METADATA of the node,if category is there it won't be null.One of the data structures has the category value.
In my blog I have several samples showing you how category metadata is parsed and updated
If you use REST API check developer.opentext.com there are methods that has similar info as well and is light weight programming
Well, if I called the wrong number, why did you answer the phone?
James Thurber, New Yorker cartoon caption, June 5, 1937
Certified OT Developer,Livelink ECM Champion 2008,Livelink ECM Champion 2010