Using Variables in Programs

Variables that hold the data in your analytic workspaces are permanent variables. These variables persist from one OLAP session to another. However, you might not need to save variables that your programs use to hold processing information while they manipulate data. So that you do not clutter your analytic workspaces with unnecessary variables, you can define temporary and local variables:

• A temporary variable has a value only during the current session. When you update and commit the analytic workspace, only the definitions of the variables are saved. When you detach the analytic workspace, the data values are discarded.
• A local variable is a single-cell variable that exists only while the program in which it is defined is running. Using local variables within a program is a useful alternative to using temporary variables.

  Local variables have no dimensions, so you cannot use them for storing dimensioned data. Because they exist only for the duration of the program in which they are defined, you cannot store information in a local variable in one program and then use that variable in another program. If you must store dimensioned data, or use information in more than one program, then define a temporary variable instead.

Global Versus Modular Design Approaches

The purpose of most OLAP DML programs is to manipulate data. Depending on your programming style and the requirements of your application, you might use either of the following approaches:

• Use permanent variables, to which all programs have access. This approach requires less programming overhead (for example, fewer definitions), but it is less modular. If you are not careful, then programs can interfere with one another when they set the values of permanent variables.
• Use program arguments, local variables, and return values from user-defined functions. This approach forces you to write modular programs with clear input and output responsibilities.

Most applications combine these approaches, using permanent variables and user-defined functions when they are appropriate. In general, modular programs are considered to be easier to read, debug, and maintain.

Defining Temporary Variables

You define temporary variables with the TEMP keyword in the DEFINE command, as in the following example.

DEFINE total.sales DECIMAL TEMP

Defining temporary variables for use in programs helps you avoid cluttering your analytic workspace with temporary data, but it still adds objects to your analytic workspace. For most simple applications, the addition of a few temporary objects is not a problem. However, in complex applications that require many programs, the number of temporary objects can sometimes get very large, and this can affect the application's performance.

Once defined, a temporary variable will exist for the remainder of a user's session unless it is deleted. Be sure to delete the temporary variable as part of the cleanup of your program, or create it on the condition that it does not already exist, so that it can be rerun during a session without causing an error.

Defining Local Variables

You must specify local variables at the beginning of your program, before any executable commands. You specify a local variable with the VARIABLE command, which has the following syntax.

VARIABLE name datatype

The name argument specifies the name of the variable. To minimize confusion or problems, you should avoid using the same name for both an analytic workspace variable and a local variable. When both an analytic workspace variable and a local variable have the same name, then the local variable usually takes precedence. However, in a few commands and functions that operate on workspace objects (for example, the OBJ function), the defined variable takes precedence.

The datatype argument specifies the data type of the local variable. For more information on data types, see "Data Types".

The program named west.rpt, listed below, includes definitions for two local variables named data and rpt.month.

DEFINE west.rpt PROGRAM
LD Produce report for Western Sales District
PROGRAM
VARIABLE data TEXT
VARIABLE rpt.month TEXT
LIMIT month TO LAST 3
   .
   .
   .