Exactly the same as llSetScriptState(string scriptName, integer running) except that it can be applied to linked primitives and thus would take the form:
llSetLinkScriptState(integer linkNum, string scriptName, integer running);
The linkNum param of course is either a single link-number or one of the LINK_* constants such as LINK_ROOT, LINK_THIS, LINK_SET etc.
The scriptName parameter is either the name of a specific script in the link(s) (if present, ignored otherwise), or it can be left blank to change the state of ALL scripts in an object.
This function would be especially useful in items which have multiple scripts that do very little (such as change colour of a prim) and are controlled centrally by root-scripts. For example, I have an 18 prim HUD which needs scripts in each button really to handle functionality, partly due to how it works and partly due to the amount of stuff it does (many of the scripts are pushing the memory limit). However, when the HUD isn't really doing anything then these scripts aren't really needed, especially if the HUD is minimised. This script can then be used to simply deactivate all other scripts (except the main one), causing any overhead they may cause to be reduced/eliminated when idle.