HP 3000 Manuals HP 3000 Manuals
MODE Command
The MODE command specifies the way files are used in the current process.
Formats
{*READ }
MODE {*WRITE } file_ref...
{*LOCK }
{*UNLOCK}
Parameters
file_ref
The name of the application data files or HP TurboIMAGE/iX data sets that
you want to specify access conditions for. Use the HP ALLBASE/4GL file
name, not the external file name.
Description
The MODE command specifies the way the application's data files are
accessed in the current process.
NOTE You can only use the MODE command in a process. It cannot be used
in a function.
Each MODE command remains in effect until another process is initiated.
You can include more than one MODE command in a process, but subsequent
MODE commands in a process will not affect the usage mode of any files
that are open at the time.
You can specify as many file references as you wish.
The command argument *READ specifies that the file or files are available
for reference purposes only. The files cannot be updated in any manner.
The *READ argument is the default condition and applies to all files not
explicitly specified in a MODE command.
The MODE command does not have any effect on HP ALLBASE/SQL table
locking.
KSAM Files
With KSAM files, the MODE *LOCK, MODE *WRITE and MODE *UNLOCK forms of
the command all perform the same function. They each specify that the
file or files are available for reading and writing. Under any of these
modes, HP ALLBASE/4GL locks the file at the first access that reads or
writes a file record. (Locking does not occur if the file access command
uses the *NOLOCK argument, and the file has not been locked by an earlier
access.)
These different forms of the MODE commands are provided to allow
application portability to and from other operating systems that allow
record based locking of indexed files.
The MODE command operates in conjunction with the FILE command to
determine the file locking procedure used by HP ALLBASE/4GL. Refer to the
FILE command (\SAM ) for a description of the HP ALLBASE/4GL file locking
system.
HP TurboIMAGE/iX Data Sets
With HP TurboIMAGE/iX files, the MODE *LOCK, MODE *WRITE, and MODE
*UNLOCK forms of the command operate also specify that the file or files
are available for reading and writing.
MODE *WRITE should be used with care. It does not guarantee any
transaction integrity, but can be used by developers without significant
knowledge of HP TurboIMAGE/iX locking. When using MODE *WRITE, a data
set level lock is placed.
The record remains locked to the current process until another record is
accessed through the same file buffer, the buffer is cleared, the file is
closed, or a FILE *UNLOCK command is executed.
NOTE When a lock is released, all locks held on the database are
released.
MODE *UNLOCK is similar to MODE *WRITE, except that a lock is not
released until a specific FILE *UNLOCK command is executed. If a data
set is locked, another user or process cannot lock the same data set
while the lock is current.
The command argument *LOCK specifies that the process has write access to
the file. Each file is locked when it is first accessed. The file or
files remain locked until the end of the process, or the files are
closed.
While a file is locked to a process that uses the *LOCK form of the MODE
command, another process or user can read the file provided that the file
is accessed under MODE *READ. However, while the MODE *LOCK command is in
effect, other processes or users cannot write to the file or lock the
file.
The MODE command and the DM IMAGE *MODE command.
The *MODE command may be used in conjunction with the DM IMAGE *MODE
command. The two commands perform similar but discrete functions. The
DM IMAGE *MODE command sets the access mode that HP ALLBASE/4GL uses to
access an HP TurboIMAGE/iX database. The access mode specifies read and
write access restrictions as well as enforcing locking requirements. The
MODE command specifies, to HP ALLBASE/4GL, the read and write permissions
for a single data set, and also specifies how HP ALLBASE/4GL should
perform implicit locking of files if no DM IMAGE *LOCK commands are used
to lock a file.
The capability provided by the MODE command must be a subset of a DM
IMAGE *MODE command.
For example, DM IMAGE *MODE *MODLOCK and MODE *READ can be used together
because reading is a subset of DM IMAGE *MODE
*MODLOCK capability, but DM IMAGE *MODE *READLCK and MODE *WRITE cannot
be used together, because the MODE command specifies more capability than
the DM IMAGE *MODE command.
If the MODE command used in conjunction with a DM IMAGE *MODE command is
not a subset of the DM IMAGE *MODE command, an error will occur at
run-time if an action is attempted that requires more capability thatn
the DM IMAGE *MODE command provides.
Example
1 MODE *WRITE stock stck_trn
This command specifies that the two files stock and stck_trn may be
updated until another process is initiated. All other files may be
accessed for reference purposes only.