TurboIMAGE/XL Database Management System Reference Manual MPE/iX V6.5 (30391-90011)

Chapter 5 231
TurboIMAGE/XL Library Procedures
DBUPDATE
list is the name of an array containing an ordered set of data item identifiers,
either names or numbers. Values supplied in the buffer array replace the
values of data items occupying the same relative position in the
list
array. The user class established when the database is opened must allow
at least read access to all the items included in the
list array.
If the corresponding buffer array values are the same as the current data
item values, the
list array can include data items to which the user has
read access only, such as, key, search and sort items. This feature permits
reading and updating with the same
list array contents. Those items to
be updated must allow write access and cannot be key, search, or sort
items.
The list array can contain a left-justified set of data item names, separated
by commas and terminated by a semicolon or a blank. No embedded
blanks are allowed and no name can appear more than once.
When referencing by number, the first element of the
list array is an
integer
n followed by n unique data item numbers (one-halfword positive
integers).
The
list not only specifies the data items to be updated immediately but
is saved internally by TurboIMAGE/XL as the current list for this data set.
The current list is unchanged until a different list is specified in a
subsequent call to DBGET, DBPUT, or DBUPDATE for the same access path
and data set.
Some special list constructs are allowed. These are described in Table 5-20.
with the DBPUT procedure. List processing is a relatively high overhead
operation that can be shortened substantially in subsequent calls by using
the asterisk construct to specify that the current list is to be used.
buffer is the name of an array containing concatenated values to replace the
values of data items occupying the same relative position in the list array.
The number of halfwords for each value must correspond to the number of
halfwords required by its type multiplied by the sub-item count. Search
and sort item values can be included in this update list if their values will
not change.
Discussion
Before performing an update for a database opened in access mode 1, TurboIMAGE/XL
verifies that locks are in effect to cover the data entry both before and after it is modified.
The current record number, forward and backward pointers are unchanged. (Refer to the
description of status words 3 through 10.)
If the process is logging, a call to DBUPDATE causes a log record to be written with such
information as the time, date, user identification number, and a copy of both the old and
new data item values.
When DBUPDATE is called within a dynamic transaction, a log record is written after the
successful completion of the physical transaction. If the intrinsic cannot be completed, an
error is returned. This error condition must be checked, and you must decide to use