The GANTT procedure divides the observations (activities) into a number of subgroups of approximately equal numbers. The size of each group is determined by the PAGESIZE system option. Similarly, the time axis is divided into a number of approximately equal divisions depending on the LINESIZE system option.

If the FILL option is specified, however, each page is filled as completely as possible before plotting on a new page. If both axes are split, the pages are ordered with the chart for each group of activities being plotted completely (the time axis occupying several consecutive pages, if needed) before proceeding to the next group.

If a BY statement is used, each BY group is formatted separately.

Two options that control the format of the chart are the MININTERVAL= and SCALE= options. The value for the MININTERVAL= option, denoted by mininterval, is the smallest time interval unit to be identified on the chart. The value for the SCALE= option, denoted by scale, is the number of columns to be used to denote one unit of mininterval. For example, if MININTERVAL=MONTH and SCALE=10, the chart is formatted so that 10 columns denote the period of one month. The first of these 10 columns denotes the start of the month and the last denotes the end, with each column representing approximately three days. Further, the INCREMENT= option can be used to control the labeling. In this example, if INCREMENT=2, then the time axis would have labels for alternate months.