IBM 3741 Data Station Reference Manual page 137

The remainder of the data set label checking is done by the
base 3741. A bypassed data set will be skipped during a
read or write data transfer; however, if the bypassed data
set is the first one to be transferred, and the operation is to
begin from the index track, the data transfer operation will
not start. The error condition which results from a bypassed
data set can be reset by the operator if so desired and pro-
cessing continued. A write-protected data set will be
skipped during a read operation; it also will prevent the start
of data transfer during a read operation if the write-protected
data set is the first data set to be transferred.
Five modes of file transfer operations can be selected for
either reading or writing:
Mode
1:
Single data set transfer
Mode
2:
Multiple data set transfer, by single data set
under operator control
Mode 3: Multiple data set transfer, continuous with
EOO indicator between data sets
Mode
4:
Multiple data set transfer, continuous with
operator-selected EOO and EOJ records
Mode 5:
Multiple data set transfer, combining consecu-
tive data sets with no EOO indicators unless
an L is entered by the operator
Each of the modes can start from the index track or from
within a data set and are initiated by the following pro-
cedure:
1.
2.
3.
Enter the device address of the system in position 1.
Enter the mode of operation (such as a 1, 2, etc) in
position 2.
a. Press FUNCT SEL upper and OUP (OUTPUT) for
a write operation, or
b. Press FUNCT SEL upper and FIELD COR (INPUT)
for a read operation.
Mode 1
The 'single data set transfer mode, using a single disk drive,
transfers data until an EOO (end of data) is encountered.
The EOO causes termination of the operation, an EOJ
(end of job) is sent, and the read/write head then returns to
the index track. The only difference between reading or
writing in mode 1 is that the read operation has to update
the EOO field in the data set label before the 3741 goes
off-line.
If the EOE (end of extent) is reached, and there is more
data to be transferred, one more record will be received
from the system and stored in program buffer
A~
An error
will be posted to indicate this condition, and the 3741 will
wait for an operator response. Holding ALPHA SH I FT and
pressing RESET, holding NUM SHIFT and pressing RESET,
or pressing RESET can be used to clear the error and will
leave the 3741 online, allowing recovery of the last record
of data. To recover the last record received and continue
processing the remainder of records, the operator can (1)
extend the data set, search to EOO, press R EC AOV, and
restart; (2) position to another data set label and continue
the operation after keying the initiating sequence; or (3)
insert another disk and follow the procedure in (2). Upon
continuation of the operation, the record saved in program
buffer A will be the first record written to the diskette. It
is the operator's responsibility not to modify or destroy
the record in program buffer A.
If holding both ALPHA SHIFT and NUM SHIFT while
pressing RESET is used to clear the previously described
soft error, the 3741 is taken offline, and the record in pro-
gram buffer 10 is lost.
The procedure for recovering the last record can also be
used in modes 2 and 5 if the EOE is reached before all of
the data has been transferred by the system.
Mode 2
This mode of operation also uses only a single disk drive.
The difference in operation between modes 1 and 2 is that
in mode 2 the 3741 does not go offline after a single data
set has been transferred, but instead remains in a wait state
expecting another data set transfer to be initiated. The read
operation again updates the data set label with the correct
EOO after each data set is transferred. Each transfer of a
data set must be reinitiated by keying a 2 in position 2 if
the transfer of data is to be continued beyond that data
set. When the data set to be transferred is the last one, key-
ing a 1 in position 2 instead of a 2 will cause the 3741 to
automatically terminate the operation with an EOJ (end of
job). However, if the last data set was transferred without
keying a 1 in position 2, the operation will have to be ter-
minated manually: by entering the device address and
pressing FUNCT SEL upper and T, which will send the EOJ
to the system and terminate the operation.
Mode 3
Mode 3 can use both disk drives. It transfers data con-
tinuously with no wait between data sets. When the EOO
is encountered, an EOO indicator is sent to the system when
writing or received from the system when reading. C in
110 Adapter 131