STATIC{(*ALLTHREAD)}

The STATIC keyword is used:

• To specify that a local variable is stored in static storage
• To specify that the same copy of a static variable will be available to all threads in a multithreaded environment
• To specify that a Java method is defined as a static method.

For a local variable of a subprocedure, the STATIC keyword specifies that the data item is to be stored in static storage, and thereby hold its value across calls to the procedure in which it is defined. The keyword can only be used within a subprocedure. All global fields are static.

The data item is initialized when the program or service program it is contained in is first activated. It is not reinitialized again, even if reinitialization occurs for global definitions as part of normal cycle processing.

If STATIC is not specified, then any locally defined data item is stored in automatic storage. Data stored in automatic storage is initialized at the beginning of every call. When a procedure is called recursively, each invocation gets its own copy of the storage.

For any variable in a module where THREAD(*CONCURRENT) is specified on the Control specification, STATIC(*ALLTHREAD) specifies that the same instance of a static variable will be used by all threads. If *ALLTHREAD is not specified for a static variable in a thread-concurrent module, then the variable will be in thread-local storage, meaning that each thread will have its own instance of the variable.

The following rules apply to the use of the STATIC(*ALLTHREAD) keyword:

• STATIC(*ALLTHREAD) is not allowed unless THREAD(*CONCURRENT) is specified on the Control specification.
• The STATIC keyword is implied for global variables. The STATIC keyword cannot be specified for a global variable unless *ALLTHREAD is specified as a parameter.
• A variable defined with STATIC(*ALLTHREAD) cannot be initialized to the address of variables which are not also defined with STATIC(*ALLTHREAD).

Caution: It is up to you to ensure that a static variable used in all threads is handled in a thread-safe manner. See the "Multithreading Considerations" section in the Rational Development Studio for i: ILE RPG Programmer's Guide, and .

Tip: It is a good idea to have a naming convention for your all-thread static variables to alert maintenance programmers and code reviewers that the variables need special handling. For example, you could add the prefix ATS_ to all your variable names that are defined with STATIC(*ALLTHREAD).

For a Java method, the STATIC keyword specifies that the method is defined as static. If STATIC is not specified, the method is assumed to be an instance method. You must code the STATIC keyword for your prototype if and only if the Java method has the "static" attribute. The *ALLTHREAD parameter is not allowed when the STATIC keyword is specified for a prototype.