Update Mode (U); Verify Mode (V); Modulus - IBM 3742 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 an M
error. However, the mode automatically changes to the
update mode when record backspacing occurs during the
enter mode. The search mode also automatically changes
to update mode at the end of a search operation. A 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.
Record is read from ........... - - -
disk into current Disk
record buffer and
displayed. Any
changes are keyed
into current record
buffer. ~
011.-
- - - - - - ' I
•
o
nm~
~~
Record advance
transfers data to
previous record buffer
and reads next record
into current record
buffer. If data was
changed, it is
written to disk.
Keyboard
Figure 10. Data Flow for Update Mode
If record advance reaches EOD during update mode, the
mode of operation automatically changes to enter mode.
However, an auto return to index track is performed if the
data set is protected by a write protect byte in the label (a
G error is displayed) or if the data set is full (an E error is
displayed) .
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
automatica'ily compared with the corresponding character
in the record in the current record buffer. If the characters
do not compare, a 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 from read index mode or update
mode, the previous record buffer is automatically filled
with blanks, and the first non-deleted record is read into the
current record buffer.
Next record is read
from disk into the ...... ' - - - - -
hold buffer.
The record is
transferred at record
Disk
advance to the current~
record buffer and
diSPlayel
Keyed data is com-
pared with the data in
DL-I _ _
----oJ
•
o
~:;:~~ :~~~~c:uffer. ~~
lIM
i f~~'"
transfers data to _ _ _ ___
1 __ _
previous record buffer.
Data written to disk Keyboard
only if data was
changed.
Figure 11. Data Flow for Verify Mode
Data Station Operating Information 11