iX V6.5 (30391-90011)

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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