If the market open interest of any stock crosses 95% of the MWPL (Market-wide positions limits), all F&O contracts of that stock enter a ban period.
Market Wide Position Limit is the total limit available for a stock across all the market participants/traders combined. MWPL for futures and options contracts on individual securities shall be 20% of the number of shares held by non-promoters in the relevant underlying security i.e. 20% of the free float in terms of the number of shares of a company.
When the stock F&O contracts are in the ban period, no fresh positions are allowed for any of the futures and options contracts in that stock. Roll-over of existing positions is also not permitted.
You will only be allowed to exit the existing positions during this period. The ban is reversed only if the open interest falls below 80%.