This operation can be performed only by users assigned the Admin role.
Proceed as follows to cancel all open limit orders placed on a specific market and forbid users to place new orders on it:
Navigate to Settings > Markets in the Admin Panel main menu.
Use the search panel displayed at the top of the screen to locate a required market (for example, LTC/BTC).
Select a list entry corresponding to the specified market and click the gear icon displayed on the right side of the row.
In the dialog window that is invoked, expand the Status drop-down list and select Halted.
Click Proceed to close the dialog window and apply the changes.