IBM 5280 Maintenance Information Manual page 85

Not Used (byte 79):
Not Used (byte 80):
Not Used (bytes 81 through 94):
System Code (bytes 95 through 107):
File Application Type (bytes 108 through 109):
Not Used (bytes 110 through 117):
Data HeaderiTrailer Label Indicator (byte 118): Used only
by I and E exchange.
Number of Data Header Labels (bytes 119 through 120):
Used only by I and E exchange.
Number of Data Trailer Labels (byte
121): Used only by
I and E exchange.
Record Delete Character (byte 122): Used only by I and
E exchange.
Pad (bytes 123 through 127): Indicates the end of this
data set header label. The pad extends to the end of the
sector. Each position of this field contains hex FF.
Theory 73