Oven cycle light stays on and will not go off. Does this means there is a problem

When the light is on, it is the heating element coming on to recover lost temperature. It is just the thermostat and the element working correctly. When the light is on, it is heating, when the light goes off, it has reached the 'set temperature'.

Nice commercial oven, I am a chef retired.

https://www.google.com/search?q=duke+e101-ev+manual

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is the light oven on??? can you see the switch/button that the door would hit against to turn light off?? if so depress button so the lifht goes off, and start a clean cycle.This should make the lock mechanism engage fully. then cancel cycle and should fully disengage lock/latch (you need to depress light switch to trick unit into thinkin the door is closed)

emerson mecrowave mw81195bm clock works but I can heat anything it doesn.t work inside

I would be interested to know just how long it is that the oven does stay lit. All ovens, gas and electric, cycle off and on throughout a baking cycle, to maintain the proper temp. If the flames or the power to the element were to stay on at full power for the life of the food's required time in the oven it would most likely wind up charred. The temp would simply continue to rise, up and up and up. If that's what it appears to be doing, then it's just working normally. If it goes out completely and stays off, doesn't come back on in a few minutes, then it may be in a keep warm mode. Many ranges have a TIMED BAKE cycle available, so you can set the clock to start the oven at such and such a time, cook the food and then shut off. Once it's finished with the cooking cycle, it goes into a keep warm mode, where it will come on for a short time and then go off, to maintain about 180 degrees. Not hot enough to really cook anything anymore, but hot enough to keep it warm for you when you get ready to eat.
If this seems to be the way it's acting, then look for the timed bake function on the console and set things back to a manual mode.

What do you mean that it wont stay on? Does it turn off and on during cooking? Does it just go off and wont come back on? The oven thermostat regulates the heat in the oven and the oven element and the oven indicator light will turn off and on during cooking. If it stayed on constantly on full oven element power everything would burn.

I assume you mean the internal oven light when you say 'bake' light. If so, the oven light you are referring to is the oven indicator light. When the element is receiving power the oven indicator light will be on. When it's not receiving power it will be off. The oven thermostat controls power to the element and the power cycles on and off during cooking so as to maintain the required temperature. This is a normal occurrence.

Two possible problems. If the oven has two or more elements for normal operation then one of these elements may be faulty. The thermostat may also be faulty and only heating to a far lesser temperature than required. The way to tell is turn the oven to a normal cooking temperature.
If the oven indicator light stays on all the time and doesn't cycle off then it may be an element problem, meaning that the oven can't reach the temperature setting desired.
If the oven indicator light goes off after a while and then cycles on and off then the thermostat is working correctly but the temperature may not be hot enough. You may have to purchase a small oven thermometer and check the oven temperature against the thermometer to get a better idea of what the problem is.

Do you mean it continues to heat, or the indicator "says" it's on ? These wall ovens have notorious problems with the erc (clock/timer) could be a relay stuck in the closed position. trip the breaker, pull out the erc and visually inspect it, or if you're really inclined check to see if the relay "cycles" (clicking on & off/open & closed) through out operating.

http://www.vikingrange.com/MEDIA_CustomProductCatalog/m20127_f20254.pdf
Go to this web site. It has a manual on Viking ovens.
Usually, when the set temp is reached, the flame will cycle down to what is called "Minimum Blaze". This is to put heat into the unit at the rate that it leaves the unit. It helps to hold temp rather than cycle off and on. It cycles high when temp goes below set and then cycles down when set temp is reached.

You don't need to do anything special.

Quoting from Daco.com FAQ

"In our ovens, the cooling and convection fans do not turn off when the oven door opens. The lights also do not turn on. There is no timed shutoff on our ovens, either, meaning that once they are turned on, they will stay on until you manually turn them off. Both of these would be considered violations. Our ovens do not have a special Sabbath button because our ovens already adhere to the laws. When the oven door is opened, there are no changes to the control panel, which would also be a violation. It is best to wait for the small "On" light with the circle around it to go on before opening the oven door, though. This light indicates that the element has gone on, as the oven cycles on and off to maintain the selected temperature. Opening the oven door without this light going on may trigger the element to go on, which can be a violation."