Thread safety

A function is threadsafe if you can start it simultaneously in multiple threads within the same process. A function is threadsafe if and only if all the functions it calls are also threadsafe.

• Storage usage and threaded applications
  When writing a threaded application, it is important to understand the visibility and scope of various classes of storage.
• Job-scoped resources and thread safety
  Many system and application resources are available only within a defined job. When writing a multithreaded application or service, you must evaluate your use of job-scoped resources. The use of these resources must not conflict with or negatively affect other threads in the process.
• API thread safety classifications
  Before using an API, you should determine if it is safe to call that API in your multithreaded program.
• CL commands and thread safety
  The Integrated Language Environment^® (ILE) CL run time and compiler-generated code are threadsafe. Original program model (OPM) CL programs are not threadsafe.
• Denied access functions and thread safety
  To prevent problems in system integrity and data damages, certain APIs and commands are either conditionally threadsafe or not threadsafe. These APIs and commands deny all or partial access.
• Exit points
  The i5/OS™ registration facility allows you to define exit points for functions in an application and to register programs that run at those exit points.