Using Global Variables › Global Variable Characteristics

Global Variable Characteristics

Understanding the characteristics of global variables can help you properly use global variables properly. All global variables have the following characteristics:

• Global variables can be as long as 32,000 bytes. However, global variables containing fewer than 44 bytes operate the most efficiently and expeditiously.
• Global variable are not declared. A global variable is created when you use a variable that contains a valid global stem.
• Global variable can trigger global events if their values change. Changing the value of a global variable triggers a global variable event unless that variable has a stem of GLOBALx. or GLVTEMPx. (where x is a number from 0 to 9).
• Global variable are not as suited to applications that need serialization, as is the OPSVALUE function.
• The OPSVALUE function (see the Command and Function Reference) enables you to manipulate global variables in many ways. Because there are so many ways to use it, you must be careful that you use the correct syntax for the task that you want to accomplish. Two of the most important syntax-critical facets of OPSVALUE are as follows:
  • OPSVALUE evaluates the derived name of your global variable differently, depending on whether it is entered with quotation marks. For example:

    var = OPSVALUE('GLOBAL.A','C' ,1,2)
    var = OPSVALUE(GLOBAL.A,'C' ,1,2)
    

    In the first case with the single quotes, OPS/REXX evaluates the first parameter as the derived name of GLOBAL.A, whereas without quotes, it evaluates the first parameter as the actual value of GLOBAL.A

  • OPSVALUE is case-sensitive when it evaluates the characters of a global variable after its stem; for example, GLOBAL.XYZ and GLOBAL.xyz are two different variables
• Global variables have derived names.
• Global variables are available to all rule-based and TSO-based OPS/REXX programs in all address spaces. You can set the value of a global variable in one rule, and then check or reset the value in another rule.