When a Cymbidium has been in a pot for a number of years and the mix breaks down, as I expect yours has done because of the large number of leafless pseudobulbs termed back bulbs (BB's), it is recommended by most growers to divide the large plant so as to have several green bulbs with one or two BB's attached in each division. Place each of these new divisions in a clean pot leaving about 2" all around the division to the edge of the pot for future plant growth. Remove the roots from the attached BB's and cut the roots on the green bulbs to about 3" from the base of the green bulb to stimulate new root growth.
Extra BB's may be started in a number of ways (see earlier discussion on this forum) to produce new plants.
CL