holding pattern
 

can a controller hold ifr traffic by defining a new holding pattern based on dme or radial instead of using existing one beacuse of traffic or congestion or something else ?if there is no radar service or airspace classification;);););):O:ok:

Yes, though it's uncommon in the UK or my bit of the desert. It is much more common in Canada, where the clearance would be somthing like:
"cleared to the XXX Vor 020 radial at 15 DME, via direct, maintain 5 thousand. Hold north east between 15 and 20 DME, right hand turns."
So, a pilot doing IR training has to have a pen handy!
If it's purely for ATC's benefit rather than for pilot training, I find it's easier to vector an aircraft into a position that works, then instruct the pilot to take up an orbit until advised.

No reason why not if you can be sure that it is terrain-safe and separated from other routes and holds and doesn't create any other hazard (and I think it's debatable whether ATC is really responsible for terrain-safety if the aircraft is not being vectored around the hold....but I'd make sure it was anyway).

Not done much in the UK because there's not much room and setting up a hold where one doesn't exist will probably take the aircraft outside CAS or conflict with some other procedure.

tis done quite often in the LTMA, albeit using radar

I've several times used a holding on 10nm final, especially during the winter when you have to close down the runway for a couple of minutes and want to have a few aircrafts ready to commence approach quickly if snow sweeping is a bit quicker than expected.

The drawback is of course that there aren't any kind of procedural separation to other holdings/routes/etc if the radar would fail. Usually not a problem since the few holding at 10nm are normally stacked below the ones holding in the regular holdings.

"XXX123, proceed direct and make a holding at 10nm final rwyYY, inbound heading YYY, 2 min racetrack, right turn"

In the UK, proceduraly, the answer is No, and even under radar control, except under exceptional circumstances, it would go against unit Safety Management System (SMS - cover the employers arse) to do so.
Aircraft should hold at a designated fix, otherwise how do you know that they are technically seperated from other aircraft.
I know that common sense says that they probably are, but unfortunately the case has to be double proven by safety cases, risk assesments and impact statements before we are allowed to use it...:rolleyes:

Does happen quite often at tc when an airport without any holding stacks(London City), has a short notice runway closure. You often have to make up your own holds and amend/cancel standing agreements to suit..