TurboIMAGE/XL Database Management System Reference Manual (30391-90012)

112 Chapter4
Using the Database
Updating Data
NOTE To avoid locking around terminal reads, you may need to establish the lock,
perform a mode 1 DBGET, check the value, update the entry, then remove the
lock.
The password you use to open the database must grant update capability to the data items
you intend to change. The user class number associated with the password must either be
in the write class list of the data set containing the items to be updated, or in both the read
class list of the data set and in the write class list of the data item.
Updating Key, Search, and Sort Items
For compatibility and security reasons, by default you cannot use the DBUPDATE library
procedure to update a master data set key item, or a detail data set search or sort item.
However, in database access mode 1, 3, or 4, you can update search or sort items if
permitted by the CIUPDATE option settings for the database and the current process; refer
to the following discussion of CIUPDATE. If you do not or cannot take advantage of the
CIUPDATE option and need to change search or sort items, or if you need to change master
data set key items, you can first delete the selected entry with DBDELETE (see the section
entitled "Deleting Data Entries"), and then add the entry back into the database with
DBPUT. However, keep in mind that this method places the new record at the end of each
unsorted chain, which disturbs the chronological order of each path.
The new entry must be complete. That is, you cannot delete an entry and then add a new
entry with only the item you want changed. If you do this, the rest of the entry will be set
to binary zeros by DBPUT. Furthermore, make sure the current list is truly current when
using an asterisk (*) to reference the list; otherwise, if items have been added or deleted,
you could cause DBPUT to write binary zeros over existing data. Note that using the
commercial "at sign" (@) to write all the items in a data entry avoids this problem.
To facilitate updates of detail data set critical items, you should design any new databases
to take advantage of the CIUPDATE option. Applications to be used with these databases
can be written as described in the next section.
Critical Item Update
TurboIMAGE/XL provides an option called critical item update (CIUPDATE) which,
depending on the settings for the database and the current process, can permit you to
update the values of detail data set search and sort items. To take advantage of this option,
you first need to set it through the TurboIMAGE/XL utility DBUTIL. Use the DBUTIL >>SET
command, and set the CIUPDATE option equal to ON or ALLOWED.
NOTE The default setting is now ALLOWED. It was DISALLOWED in releases before
C.07.00.
The ON setting permits any process to use critical item update on the database unless the
process explicitly disables the option by calling the DBCONTROL procedure in mode 6; this
call disables the option for the duration of the process or until a call to DBCONTROL in mode
5 enables the option. The ALLOWED setting requires that a process first call DBCONTROL in
mode 5 to enable the CIUPDATE option for the duration of the process or until a call to