ALLBASE/SQL FORTRAN Programs

• 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.

• Identify FORTRAN variables referenced in SQL commands, known as host variables.

• Set up a common block, known as the SQL Communications Area (SQLCA), for communicating the status of executed SQL commands to your program.

• Optionally automate program flow based on SQLCA information.

• Identify cursor declarations.

Program Structure

The following skeleton program illustrates the relationship between FORTRAN statements and embedded SQL commands in an application program. SQL commands may appear in a program at locations indicated by boldface notations. The SQLCA Common Block Declaration may appear either before or after the FORTRAN type declaration section. The SQLCA Common Block Declaration must appear, however, before the host variable declaration section which must be the last of the type declarations in the program unit. Refer to Chapter 3 for further clarification of program structure.

   PROGRAM ProgramName

   FORTRAN Statements

   .

   .

   .

   SQLCA Declaration

   FORTRAN Type Declarations

   Host Variable Declarations

   .

   .

   .

   FORTRAN Statements, some containing SQL Commands

   .

   .

   .

   END

   SUBROUTINE SubroutineName

   FORTRAN Statements

   .

   .

   .

   SQLCA Declaration

   FORTRAN Type Declarations

   Host Variable Declarations

   .

   .

   .

   FORTRAN Statements, some containing SQL Commands

   .

   .

   RETURN

   END

To delimit SQL commands for the preprocessor, each SQL command is prefixed by EXEC SQL:

   EXEC SQL BEGIN WORK

SQL commands may appear in the main program or any subprogram unit 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 runtime. In this example, the environment is SomeDBE which is in the group and account SomeGroup.SomeAcct.

   :RUN PSQLFOR.PUB.SYS; INFO = "SomeDBE.SomeGroup.SomeAcct"

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 command terminates that session.

   SUBPROGRAM Unit

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   .

   .

   EXEC SQL CONNECT TO 'SomeDBE.SomeGroup.SomeAcct'

   .

   .

   .

   EXEC SQL RELEASE

   RETURN

   END

At runtime, the program starts a DBE session in SomeDBE.SomeGroup.SomeAcct, 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 9 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. 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 file, ALLBASE/SQL stores a module for that program file 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 file.

To run a program accessing an ALLBASE/SQL DBEnvironment, you need the following authorities:

At runtime, any SQL command in the program, except for the command used to start the DBE session, is executed only if the OWNER of the module has the authorization to execute the command at runtime. However, any dynamic command is executed only if the individual running the program has the authority to execute the command at run time. A dynamic command is an SQL command entered by the user at runtime.

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. 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 is created with the following command:

   START DBE 'PartsDBE' NEW

and the user is currently in the SQL group of the DBSUPPORT account, the file name PARTSDBE.SQL.DBSUPPORT is stored in the DBECon file. If the user subsequently creates 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 with the name ORDERSFS.SQL.DBSUPPORT. If however, the user creates a DBEFile with the command:

   CREATE DBEFILE ORDERS WITH PAGES=50, NAME='DBSUPPORT'

the name stored in the DBECon file is ignored while creating this file. The user then needs to fully qualify this file name each time the file is referenced. Remember, a file, group, or account name can contain a maximum of 8 bytes. Fully qualified file names, enclosed in quotes, are restricted to a maximum length of 36 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 PSQLFOR.PUB.SYS;INFO = 'SOMEDBE.SQL.DBSUPPORT'