IBM 3741 Data Station Reference Manual page 79

End of Extent: The end of extent (EOE) address is made
equal to the record address of the last recorded record.
End of Data: The end of data (EOO) is made equal to the
end of extent plus 1, except when a null data set is received.
In this case, the end of data and end of extent are made
equal to the beginning of extent address.
Multivolume Indicator: The multivolume indicator of the
first disk is changed to a C (continued data set) when the
overflow of the first disk is written on the second disk.
The multivolume indicator of the second disk is changed
to an L to indicate the last disk of a continued data set.
All other label information is left unchanged.
If the operator desires to start recording received data
from any position on the first disk, the operator can
position the disk to any record of any data set with normal
key entry operations, and subsequently start receiving and
recording data from that disk position.
If one or two disks of data are received with no errors, an
RC is displayed on the display's status line to indicate a
completed reception of data.
If a disk error occurs or if the disk(s) is full, then RJ will be
displayed on the display's status line. The 3741 will not
automatically answer a telephone call if the mode indicator
indicates RC or RJ. For RC, the operator can check status
and mount new diskettes. For RJ, the operator must
correct or bypass the error condition in order to continue
receiving data.
If the mode indicator remains R (as it would in a line check,
remote abort, or a length check occurred), the 3741 will
answer a telephone call and will receive the data beginning
at the same place as the original call. However, on early
shipments of the 3741 Model 2, if communications mode
was selected with a data set record displayed, the operator
must reposition the disk to the original starting position.
Your 3741 can be field upgraded so that the operator does
not have to reposition the disk to the original starting posi-
tion. Contact your I BM representative for more informa-
tion. If your 3741 has not been field upgraded and you
are performing unattended operations, it is recommended
that the communications mode be selected while the label
is displayed.
Notes:
1. SOH, STX, or OLE STX in non-transparent or OLE STX
(when not immediately preceded by a OLE) in trans-
parent text will be recognized as control characters and
will be deleted from the text. Other BSC products may
not prohibit the transmission of these control characters
in text even though such characters are not supposed to
be in text.
2. The following characters cannot be received as data in
the non-transparent mode: SOH, STX, ETX, ETB, EOT,
ENO, OLE, NAK, ITB, and I RS (only for expanded
communications) .
With the expanded communications feature in receive mode,
the 3741 has the capability of receiving non-transparent
transmission blocks containing up to 512 bytes of data and
I RS characters. Each record must be separated by I RS char-
acters if more than one record per transmission block is to
be received. Records can be spanned between two trans-
mission blocks. Transmission block lengths must be greater
than the length of each record, except for the last trans-
mission block of the data set. One record per transmission
block in either transparent or non-transparent text can also
be received with the expanded communications feature.
When the transmission block length equals the record
length, no I RS character is required. The first IRS, ETX,
or ETB (OLE ETB or OLE ETX in transparent text) of the
first transmission block determines the record length for
records in that data set. An I RS character preceding the
ETX or ETB character is mandatory on all multiple record
transmission blocks except the last block.
For the receive portion, up to 512 bytes per block can be
received. Each record within the data set being received
must be the same length. Records must be separated by
I RS characters if more than one record per transmission
block is to be received. Records can be spanned between
two transmission blocks. Transmission block lengths must
be greater than the length of each record, except for the
last transmission block of the data set.
The receive operation can also receive one record per trans-
mission block in either transparent or non-transparent text.
When the transmission block length equals the record length,
no I RS character is required.
The first IRS, ETX, or ETB (OLE ETB or OLE ETX in trans-
parent text) character of the first transmission block deter-
mines the record length for records in that data set. IRS
prior to ETX or ETB is mandatory for all multiple record
blocks except the last block.
Communications 73