HP 3000 Manuals HP 3000 Manuals
RDBA Access Methods
There are three ways to open a remote TurboIMAGE database within a
program:
* Identify the database as a remote file in a prior FILE command; for
example, FILE dbname=dbname:envID ;
* Use the COMMAND intrinsic to include the FILE command information in
your program;
* Create a database-access file that supplies the FILE command, a
DSLINE command, and a REMOTE HELLO command.
When the file specified in a FILE command is a remote database, the
syntax (for the first two methods) is the same as it is for a remote
file; you can specify the location of the database in the formal or
actual designator or in the DEV= option. When using the third method,
creating a database-access file, the FILE command may specify a remote
database location only in the DEV= option - not in the formal or actual
designator. (For details see the description of the FILE command in the
"Remote File Access" chapter of this manual.)
With all three access methods you must call the DBOPEN intrinsic within
the program to open the remote database. In the first two cases you call
DBOPEN with the database root file name supplied in the FILE command. In
the third case you use the database-access file name.
In the first case a user needs to know the location of the database. The
application program that accesses the database does not need to have this
information. The second case embeds the information in the application
and frees the user from the responsibility of knowing the location. The
third case insulates both the user and the application program from the
information.
The COMMAND intrinsic allows a program to execute MPE XL commands. The
first parameter of the intrinsic is a string of characters giving a
specific command. You can issue a series of COMMAND calls within your
program to establish a remote session ( DSLINE and REMOTE HELLO
commands) and identify the remote database (FILE command). You can then
call DBOPEN to open the database. When you have called DBCLOSE to close
the remote database, you must call COMMAND again to execute REMOTE BYE
and DSLINE;CLOSE commands. See the MPE XL Intrinsics Reference Manual
for a detailed explanation of the COMMAND intrinsic.
A database-access file contains a FILE command, a DSLINE command, and
one or more remote logon commands. When you call DBOPEN with the name
of this file, the remote session is established and the remote database
is opened. You can then call other TurboIMAGE intrinsics to perform the
desired operations upon the database.
The database-access file has the following general format:
FILE dbname;DEV= envId#
DSLINE envid
locuser.locacct=HELLO remuser.remacct
More than one local/remote logon sequence equation may be included in the
file. When you call DBOPEN with the database-access file name, a remote
session is established for the remote user that has been "equated" with
your local logon name. (An @ sign in the remote user, account, or group
name position on the right side of an equation is automatically replaced
by the corresponding local name on the left. An @ sign in a local name
position on the left is replaced by the name you actually used when you
logged on.)
Under the database-access file method, the remote session is released
automatically when the database is closed (with or without an explicit
DBCLOSE call).
Before you can reference a database-access file in a program, you have to
ACTIVATE it by means of the DBUTIL utility program. At the MPE XL
prompt, type the following command (user input is underlined):
RUN DBUTIL.PUB.SYS
>>ACTIVATE dbaccessfilename
VERIFICATION FOLLOWS:
FILE COMMAND: LOOKS GOOD
DSLINE COMMAND: LOOKS GOOD
HELLO COMMAND: LOOKS GOOD
ACTIVATED
>>EXIT
DBUTIL checks to see that the file has a file code of zero, is an
unnumbered, ASCII file, has a record length not greater than 128
characters, and contains at least three records. In order to edit the
database-access file or prevent programs from referencing it, you must
issue a DEACTIVATE command within the DBUTIL program.
One of the benefits of the database-access file method is that it
restricts who may use the database and thereby enhances security. (The
contents of the database-access file itself can be hidden from the user
who simply runs the application program.) Under this method, however,
you can access only one database in any one remote session. Under the
other two methods, you can access more than one database by means of
multiple FILE commands.
You can use QUERY , Hewlett-Packard's interactive database inquiry
facility, to retrieve information from a remote database. You could run
QUERY.PUB.SYS locally, specifying either the database name itself or the
appropriate database-access file name. If you use the actual database
name, you must have previously established a session on the remote node
and issued a FILE command for the remote database.
It is more efficient to run QUERY directly in the remote environment. At
the MPE XL prompt, type the following commands (user input underlined):
DSLINE LEO
REMOTE HELLO NSUSER.NSACCT
REMOTE RUN QUERY.PUB.SYS
>DATA-BASE=databasename
For more information on TurboIMAGE and QUERY, see the TurboIMAGE Data
Base Management System Reference Manual, especially the sections entitled
"Using a Remote Database;" and also see the QUERY/3000 Reference Manual.