iX V6.5 (30391-90011)

Chapter 4 95

Using the Database

Opening the Database

(63 per database) depending on the availability of system resources. The DBUX

remains allocated until the user's process is terminated.

• The TurboLock Table is a permanent ﬁle, TURBOLKT.PUB.SYS, that is created by

DBOPEN (if it does not exist beforehand). Thereafter, it is opened when the ﬁrst user

opens any database on the system. It is purged when the system is rebooted. Each

system has only one TURBOLKT ﬁle. It is used to avoid deadlocks for all IMAGE/SQL

users. Additionally, it is also used to detect potential deadlock for TurboIMAGE/XL

users if, and only if, deadlock detection is activated by DBCONTROL mode 7.

• The Global Dynamic Multi-database Transaction Table is a permanent ﬁle,

TURBOGTX.PUB.SYS, that is created by DBXBEGIN (if it does not exist beforehand).

Thereafter, it is opened for all users who employ dynamic multi-database transaction(s)

(DMDBX). Each system has only one TURBOGTX ﬁle, and it remains on the system even

after the system is rebooted. It is used for tracking DMDBX.

• The DBQUIESCE and DBOPEN Table, QOPEN, is an unnamed global object and is ﬁrst

created by DBOPEN when the ﬁrst writer of any database enabled for user logging opens

a database. It is subsequently accessed only by writers of databases enabled for user

logging. Each system has only one QOPEN table, and it is purged when all processes

accessing it are terminated. It contains information pertaining to DBOPEN and user

logging process. This information is used to write to log records for DBRECOV and to

coordinate with DBQUIESCE called by TurboSTORE/iX 7x24 True-Online Backup.

• The DBQUIESCE LOCK Table, QLOCK, is an unnamed permanent global structure that

is created by DBOPEN (if it does not exist beforehand). There is one per system, and it is

accessed by all writers to all databases. It is purged only at system reboot time. It is

used for containing database information required to quiesce database(s) for

TurboSTORE/iX 7x24 True-Online Backup.

All TurboIMAGE/XL intrinsics process on the DBU except accesses for global and buffer

area information found in the two global blocks (DBG and DBB).

Passwords

When you open the database you must provide a valid password to establish your user

class number. If you do not provide one, you will be granted user class number 0. If you

are the database creator and supply a semicolon as a password, you are assigned user class

64, which grants you unlimited database access privileges. Passwords and user classes are

discussed in chapter 2.

Database Access Modes

There are eight different access modes for opening the database with the DBOPEN

procedure. Each mode determines the type of operation that you can perform on the

database, as well as the types of operations other users can perform concurrently. To

simplify the deﬁnition of the various DBOPEN modes, the following terminology is used:

• Read access modes (5, 6, 7, and 8) allow the user to locate and read data entries.

• Update access mode (2) allows read access and permits the user to replace values in

all data items except master data set key items and detail data set search and sort

items. The critical item update (CIUPDATE) option, which can permit the values of