When you retrieve data for editing, the editor determines whether it contains sequence numbers. The editor always examines the standard sequence field. It examines the COBOL sequence field if the data set type (the lowest level qualifier in the data set name) is COBOL.

If all lines contain numeric characters in either the standard or COBOL sequence field positions, or both, and if the numbers are in ascending order, the editor assumes the data is numbered and turns on number mode. Otherwise, the editor turns off number mode.

If the first setting of the number mode differs from the setting in the edit profile, a message indicating that the editor has changed the mode is displayed. For new members or empty sequential data sets, the first setting of number mode is determined by the current edit profile. For a new edit profile, the default is NUMBER ON for standard sequence fields, and NUMBER ON COBOL if the data set type is COBOL.