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

186 Chapter5
TurboIMAGE/XL Library Procedures
DBGET
list is the name of an array containing an ordered set of data item identifiers,
either names or numbers. The values for these data items are placed in the
array specified by the buffer parameter in the same order as they appear
in the list array.
The list array can contain a left-justified set of data item names, separated
by commas and terminated by a semicolon or 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 which is followed by n unique data item numbers (one-halfword
positive integers).
The list not only specifies the data items to be retrieved 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 which can be shortened in subsequent calls by using the asterisk
construct to specify that the current list is to be used. Use of this
construct can save considerable processing time. However, be sure a
current list exists before using the asterisk or TurboIMAGE/XL will
assume a null list. If a DBCLOSE mode 2 is used after DBGET, using the
asterisk construct, TurboIMAGE/XL uses the previously defined item list.
buffer is the name of the array to which the values of data items specified in the
list array are moved. The values are placed in the same order as specified
in the list array. The number of elements occupied by each value
corresponds to the number required for each data type multiplied by the
sub-item count.
argument is ignored except when mode equals 4, 7, or 8.
If mode is 4, argument contains a word record number of the entry to be
read.
If mode is 7 or 8, argument contains a key item value for the master data
set referenced by dset.
Discussion
The internal backward and forward pointers for the data set are replaced by the current
path's chain pointers from the entry just read. If the data set is a master, and not a B-Tree
index, they are synonym chain pointers (refer to chapter 10). If it is a detail with at least
one path, the current path is the one established by the last successful call to DBFIND;or,if
no call has been made, it is the primary path. If there are no paths defined, the internal
pointers are set to zeros.
The location of the entry just read becomes the current record for the data set. DBGET mode
5 or 6 will reread the current record and will try to continue the chain read if it encounters
a broken chain.