Globals
A global is a special kind of variable that is automatically stored within the InterSystems IRIS database. It is mapped to a specific namespace, and can only be accessed within that namespace, unless an extended reference is used. A global can be accessed by any process. A global persists after the termination of the process that created it. It persists until explicitly deleted.
Within ObjectScript code, you can use a global in the same way as any other variable. Syntactically, a global name is distinguished by an initial caret (^) character:
SET mylocal = "This is a local variable"
SET ^myglobal = "This is a global stored in the current namespace"
For complete information on names, see Rules and Guidelines for Identifiers. Briefly:
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The first character after the caret must be either a letter or the percent (%) character.
Global names starting with ^% are known as “percent variables” and are available in all namespaces. In your code, for these variables, start the name with ^%Z or ^%z; other names are reserved for system use.
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The second and subsequent characters of a global name may be letters, numbers, or the period character. A period cannot be used as the first or last character of the name.
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Unlike local variables, no global name can contain Unicode letters — letter characters above ASCII 255. Attempting to include a Unicode letter in a global name results in a <WIDE CHAR> error.
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Global names are case-sensitive.
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A global name must be unique within its namespace.
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Global names are limited to 31 characters, exclusive of the prefix characters. You may specify a name longer than 31 characters, but only the first 31 characters are used. Therefore, a global name must be unique within its first 31 characters.
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Like other variables, globals can take subscripts. See Rules About Subscripts.
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Some global names are reserved for InterSystems use. See Global Variable Names to Avoid.
It is possible to use an extended reference to refer to a global in another namespace. The syntax uses a pair of vertical bars or square brackets immediately after the caret characters (for example: ^|"samples"|myglobal or ^|""|myglobal). These syntaxes should not be confused with process-private globals.
For more information on globals, refer to Using Globals.
