HP 3000 Manuals HP 3000 Manuals
ALLBASE/SQL COBOL Programs
To write a COBOL application that uses an ALLBASE/SQL database, you embed
SQL commands in the COBOL source wherever you want the program to:
* Start or terminate a DBEnvironment session, either in single-user
mode or multiuser mode.
* Start or terminate a transaction.
* Retrieve rows from or change data in tables in a database.
* Create or drop objects, such as indexes or views.
You also embed special SQL commands known as preprocessor directives.
The COBOL preprocessor uses these directives to:
* Identify COBOL variables referenced in SQL commands, known as host
variables.
* set up a special variable known as the SQL Communications Area
(SQLCA) in the main program, for communicating the status of
executed SQL commands to your program.
* Generate error-handling code for SQL commands.
* Identify cursor declarations.
Program Structure
The following skeleton program illustrates the relationship between COBOL
statements and embedded SQL commands in an application program. SQL
commands may appear in a program at locations highlighted.
IDENTIFICATION DIVISION.
PROGRAM-ID. ProgramName.
COBOL Statements
.
.
.
DATA DIVISION.
FILE SECTION.
Host Variable Declarations
COBOL Statements
.
.
.
WORKING-STORAGE SECTION.
SQLCA Declaration
Host Variable Declarations
COBOL Statements
.
.
.
LINKAGE SECTION.
SQLCA Declaration
Host Variable Declarations
COBOL Statements
.
.
.
LINKAGE SECTION.
SQLCA Declaration
Host Variable Declarations
COBOL Statements
.
.
.
PROCEDURE DIVISION.
.
.
.
COBOL Paragraphs, some containing SQL Commands
.
.
.
STOP RUN.
To delimit SQL commands for the preprocessor, you put the prefix EXEC SQL
and the suffix END-EXEC around each SQL command:
EXEC SQL BEGIN WORK END-EXEC.
Most SQL commands appear within the Procedure Division where you
establish DBEnvironment access and manipulate data in a database.
DBEnvironment Access
You must always specify a DBEnvironment at preprocessing time. The
preprocessor needs to access the DBEnvironment you specify in the INFO
string. It does so in order to store a module containing permanent
sections used by your application program at run time. In this example,
the DBEnvironment is PartsDBE which is in the group and account
GROUPDB.ACCTDB.
:RUN PSQLCOB.PUB.SYS; INFO = 'PartsDBE.GroupDB.AcctDB'
Your application program needs to access the DBEnvironment to perform its
work. The CONNECT command starts a DBEnvironment session for a specific
environment. The RELEASE statement terminates that session.
PROCEDURE DIVISION.
.
.
.
EXEC SQL CONNECT TO 'PARTSDBE.GROUPDB.ACCTDB' END-EXEC.
.
.
.
EXEC SQL RELEASE END-EXEC.
STOP RUN.
At run time, the program starts a DBE session in PARTSDBE.GROUPDB.ACCTDB,
where a module for the program has been stored.
A program can accept a DBEnvironment name from the program user and
dynamically preprocess the SQL command that starts a DBEnvironment
session. Refer to Chapter 10 for more information on dynamically
connecting to a database and refer to Chapter 4 for more information on
using a host variable to connect to a database.
No matter how you access a DBEnvironment (dynamic or stored sections),
you must always specify a DBEnvironment name when you preprocess.
In some cases an ALLBASE/SQL program is used with one or more
DBEnvironments in addition to the DBEnvironment accessed at preprocessing
time. In these cases, you use ISQL to install the installable module
created by the preprocessor into each additional DBEnvironment accessed
by your program. You can also preprocess the same application repeatedly
with different DBEnvironments. See Chapter 2 for information on the
installable module.
An alternative method of accessing more than one DBEnvironment from the
same program would be to separate the program into separate compilable
files. Each source file would access a DBEnvironment. In each file you
start and terminate a DBE session for the DBEnvironment accessed. You
then preprocess and compile each file separately. When you invoke the
preprocessor, you identify the DBEnvironment accessed by the source file
being preprocessed. After a file is preprocessed, it must be compiled so
that no linking is performed before the next source file is preprocessed.
When all source files have been preprocessed and compiled, you link them
to create the executable program.
Note that a program which accesses more than one DBEnvironment must do so
in sequence. Such program design may adversely affect performance and
requires special consideration.
To preprocess or to use an already preprocessed ALLBASE/SQL application
program, you must satisfy the authorization requirements for each
DBEnvironment accessed.
Authorization
ALLBASE/SQL authorization governs who can preprocess, execute, and
maintain a program that accesses an ALLBASE/SQL DBEnvironment.
To preprocess a program for the first time, you need CONNECT or DBA
authority in the DBEnvironment your program accesses. When you
preprocess a program, ALLBASE/SQL stores a module for that program in the
DBEnvironment's system catalog and identifies your User@Account as the
owner of that module. Subsequently, if you have OWNER or DBA authority,
you can re-preprocess the program.
To run a program accessing an ALLBASE/SQL DBEnvironment, you need the
authority to start the DBE session in the program:
* If the program uses a CONNECT command to start a DBE session, you
need CONNECT authority and RUN or module OWNER authority to run
the program.
* If the program uses a START DBE command to start the DBE session,
you need DBA authority to run the program.
Any SQL command in the program is executed only if the OWNER of the
module has the authorization to execute the command at run time, and the
individual running the program has RUN authority for it. However, any
dynamic command is executed only if the individual running the program
has the authority to execute the command at run time. (Chapter 10
contains information about dynamic commands.)
Maintaining an ALLBASE/SQL program includes such activities as modifying
a program in production use and keeping runtime authorization current as
program users change. For these activities, you need OWNER authority for
the module or DBA authority. More on this topic appears later in this
chapter under "Maintaining ALLBASE/SQL Programs."
File Referencing
When you create a DBEnvironment, a Database Environment Configuration
(DBECon) file is created. The file name of this DBECon file is stored in
the DBECon file itself. The group and account name at creation time are
part of the DBECon file name. In all subsequent references to files, you
may use either a fully qualified file name or a file name relative to
that of the DBECon file. For example, if a DBEnvironment was created
with the following command:
START DBE 'PARTSDBE' NEW
and the user was currently in the SQL group of the DBSUPPORT account, the
file name PARTSDBE.SQL.DBSUPPORT would be stored in the DBECon file. If
the user were subsequently to create a DBEFile with the command:
CREATE DBEFILE ORDERS WITH PAGES=50, NAME='ORDERSFS'
the ORDERSFS file is created in the same group and account as the DBECon
file and would be ORDERSFS.SQL.DBSUPPORT. If however, the user were to
create a DBEFile with the command:
CREATE DBEFILE ORDERS WITH PAGES=50, NAME='ORDERSFS.SHIPPING.DBSUPPORT'
the name stored in the DBECon file would be ignored while creating this
file. The user would need to fully qualify this file name each time the
file is referenced. Fully qualified file names, enclosed in quotes, are
restricted to a maximum length of 36 bytes. The maximum length of
unquoted file names is 8 bytes.
In addition, if the DBEnvironment you want the preprocessor to access
resides in a group and account other than your current group and account,
you will have to qualify the name of the DBEnvironment.
For example, if the DBEnvironment you want the preprocessor to access
resides in the SQL group of account DBSUPPORT, you would invoke the
preprocessor as follows:
:RUN PSQLCOB.PUB.SYS;INFO = 'SOMEDBE.SQL.DBSUPPORT'