The structure of the operation region has been studied in the HT-7 superconductingtokamak, and progress on the extension of the HT-7 ohmic discharge operation region isreported. A density corresponding to 1.2 times the Greenwald limit was achieved by RFboronization. The density limit appears to be connected to the impurity content and theedge parameters, so the best results are obtained with very clean plasmas and peakedelectron density profiles. The peaking factors of electron density profiles for differentcurrent and line averaged densities were observed. The density behaviour and the fuellingefficiency for gas puffing (20-30%), pellet injection (70-80%) and molecular beaminjection (40-50%) were studied. The core crash sawteeth and MHD behaviour, which wereinduced by an injected pellet, were observed and the events correlated with the changeof current profile and reversed magnetic shear. The MARFE phenomena on HT-7 aresummarized. The best correlation has been found between the total input ohmic powerand the product of the edge line averaged density and Zeff. HT-7 could be easily operatedin the high density region MARFE-free using RF boronization.