General thread considerations

To see the advantages and disadvantages of the two types of thread-safety for RPG, see the section on multithreaded applications in Rational Development Studio for i: ILE RPG Programmer's Guide. For a list of system functions that are not allowed or supported in a multithreaded environment, see the Multithreaded Applications document under the Programming topic at the following URL: 
http://www.ibm.com/systems/i/infocenter/

You cannot use the following in a thread-safe program:

  • *INUx indicators
  • External indicators (*INU1 - *INU8)
  • The LR indicator for the CALL or CALLB operation

When using the THREAD keyword, remember the following:

  • It is up to the programmer to ensure that storage that is shared across modules or threads is used in a thread-safe manner. This includes:
    • Storage explicitly shared by being exported and imported.
    • Storage shared because a procedure saves the address of a parameter or a pointer parameter, or allocated storage, and uses it on a subsequent call.
    • Storage shared because STATIC(*ALLTHREAD) was specified on the definition of the variable.
  • If shared files are used by more than one language (RPG and C, or RPG and COBOL), ensure that only one language is accessing the file at one time.