Update Mode (U); Verify Mode (V) - IBM 3741 Data Station Reference Manual

Update Mode (U)
Use the update mode to read records from the disk for
review or modification. To select the update mode, press
FUNCT SEL lower and then press UPDATE.
Data flow is summarized in Figure 10. Update mode can be
selected from the read index, search, or verify mode. If
update is selected from the index track, the disk is posi-
tioned at BOE; if update is selected from the verify mode,
the record at the current disk address is reread. Selecting
the update mode from the enter mode results in a mode
selection (M) error. However, the mode automatically
changes to the update mode when record backspacing
occurs during the enter mode. The search mode also auto-
matically changes to update mode at the end of a search
operation. An empty data set (Y) error occurs if update
mode is selected when the end-of-data address equals the
beginning-of-extent address; in other words, when the data
set is empty.
If record advance reaches EOD during update mode, the
mode of operation automatically changes to enter mode.
However, an automatic return to index track is performed
if the data set is protected by a write protect byte in the
label (a write protect, G, error is displayed) or if the data
set is full (an end of extent, E, error is displayed).
DL--I
_ - I
•
o
Record is read from ..... ' - - - - ... - - - - - - -
disk into current Disk
record buffer and
displayed. Any
changes are keyed
into current record
-----t~
buffer.
~
(
n: ]
ACM[(ORPQRATIOh
l
Display
Record advance
transfers data to Keyboard
"
1
~
previous record buffer
---------------1
and reads next record
into current record
buffer. If data was
changed the record is
written to disk.
Figure 10. Data Flow for Update Mode
Verify Mode (V)
Use the verify mode to check the accuracy of data records
already on the disk and to make corrections to the records
when errors are found. The process of verifying data is
similar to that of entering data. As the data for a record
is rekeyed from the source document, each character is
automatically compared with the corresponding character
in the record in the current record buffer. If the characters
do not compare, a verify mismatch (V) error occurs.
To select the verify mode, press FUNCT SEL lower and
then press VERI FY. Select the verify mode from read
index or update mode. For data flow, see Figure 11. When
verify mode is selected, the previous record buffer is auto-
matically filled with blanks, and the first non-deleted record
is read into the current record buffer.
Verify mode can also be selected from verify mode.
Selecting verify mode from verify mode is provided in the
event that the operator discovers, after making some cor-
rections to the record being displayed, that the wrong
source record is being used to verify the record being
displayed. By selecting verify mode from verify mode, all
changes made to the record are ignored and the entire
record is redisplayed.
Next record is read
from disk into the
...... f - - - - - -
hold buffer.
~
.
The record
IS
transferred at record
advance to the current ____
.~I
record buffer and
displayed.
t
Keyed data is com-
pared with the data in the
01 ____ --'
•
o
Disk
Display
~u:::~; :~~~~~:uffer. ~ z-w~~<
transfers data to _ . _.
~
previous record buffer.
Data is written on the disk Keyboard
only if data was
-.-;.-----------1
changed.
Figure 11. Data Flow for Verify Mode
Operation Modes and Considerations 13