Editing size fields in variable-length segments

Variable-length segments begin with a 2-byte binary numeric size field. In SNGL or TABL display format, if you change the value of the size field, and the new value is within the minimum and maximum lengths allowed for the segment, then FM/IMS changes the segment length to match the new value. However, if the new value is less than the minimum allowed segment length (the length of the sequence field, if any, plus 2 bytes for the size field itself) or greater than the maximum allowed segment length (as defined in the DBD), then FM/IMS displays an error, does not change the segment length, and restores the size field to its previous value.