HP 3000 Manuals HP 3000 Manuals
DBLOCK
The DBLOCK statement applies a logical lock to a database, a data set, or
a data item value to all but one user. Then, the user can write to the
locked area. The PREDICATE statement aids in locking database items in
DBLOCK modes five and six. Without the PREDICATE statement, the PACK
statement must be used to build a predicate string for the DBLOCK
statement.
Syntax
DBLOCK dbname$ [, MODE [=] lock_mode]
[ {DATASET [=] dataset }]
[, {DESCRIPTOR [=] str_expr}]
[, STATUS [=] status_array(*)]
Parameters
dbname$ A string variable whose value is a TurboIMAGE database
name. dbname must be the variable that was passed to a
successful DBOPEN.
lock_mode Evaluates to an integer indicating the type of locking
desired:
Code Effect
1 (default) Locks database unconditionally
2 Locks database conditionally
3 Locks data set unconditionally
4 Locks data set conditionally
5 Locks data item entry unconditionally
6 Locks data item entry conditionally
If a data item is locked unconditionally in mode 5, the
entry for that item does not have to exist for the lock
to succeed.
dataset A string expression with a maximum length of 16
characters. Its value is the name of a data set. The
name must be left-justified and if shorter than 16
characters must be terminated by a semicolon or blank.
This parameter can also be an integer or short integer
corresponding to the desired dataset number. Required
only if lock_mode is three or four.
str_expr A string expression that is required only if lock_mode
is five or six. Its value is a predicate lock string
that describes the locking condition. The PREDICATE
statement is used to set up the predicate lock string.
The format of the PREDICATE lock descriptors is
presented in the description of the DBLOCK library
procedure in the TurboIMAGE/XL Database Management
System.
status_array A 10-element short integer array to which TurboIMAGE
returns an error code. If an HP Business BASIC/XL
database statement specifies the STATUS option, an error
does not abort the program. Following execution of the
database statement the program can check status_array
and handle the error. The values returned by TurboIMAGE
to this array are detailed in the description of the
status parameter of the equivalent TurboIMAGE library
procedure.
Examples
The following examples show the use of the DBLOCK statement. In line 30,
a PREDICATE statement has been issued for use with lines 150 and 160.
30 PREDICATE Pred$ FROM Ds$ WITH Item$="skates"
100 DBLOCK Db$,STATUS=S(*)
110 DBLOCK Db$,MODE=1,STATUS=S(*)
120 DBLOCK Db$,MODE=2,STATUS=S(*)
130 DBLOCK Db$,MODE 3,DATASET Ds$,STATUS S(*)
140 DBLOCK Db$,MODE 4,DATASET Ds$,STATUS S(*)
150 DBLOCK Db$,MODE 5,DESCRIPTOR Pred$,STATUS S(*)
160 DBLOCK Db$,MODE 6,DESCRIPTOR Pred$,STATUS S(*)