The heart of the IRAC2b online reduction system is the Observation Summary Table (OST). This table contains the essential details, such as the filter used, the lens used, the exposure etc., of every image taken with the camera. It is continuously updated as new exposures are made. For IRAC2B the table is called irac2b_ost.tbl and it is a regular MIDAS table. The contents of the table can be displayed or printed with the usual MIDAS table commands or with the OBSLIST/IRAC2 and OBSREP/IRAC2 commands described below. For a general description of OSTs and the DO context, see Chapter 15 in Volume B of the MIDAS users manual.