Basic link-editing and running PL/I MTF applications under z/OS UNIX

SIBMTASK is provided to create the main executable program for PL/I MTF applications. SIBMTASK must be concatenated before SCEELKED when the main executable program is created, whether you are creating a new PL/I MTF application or relink-editing an existing OS PL/I routine with Language Environment. SIBMTASK replaces PLITASK under OS PL/I. If the main executable program of your application is link-edited with SIBMTASK or OS PL/I PLITASK, but does not use multitasking functions, you might notice some performance loss during initialization and termination. The same releases of OS PL/I executable programs are supported by multitasking as well as nonmultitasking applications. The OS PL/I shared library support is the same for both multitasking and nonmultitasking applications.

PL/I multitasking follows the Language Environment program management model discussed in Program management model. PL/I MTF supports a single Language Environment process within an address space, and is supported in the initial enclave only. If a PL/I multitasking application contains nested enclaves, the initial enclave must contain a single task. Violation of any of these rules is not diagnosed and is likely to cause unpredictable results.

The POSIX(ON) runtime option is not supported for a PL/I MTF application and therefore no programs, including assembler programs, in the application can invoke any POSIX functions. If POSIX(ON) is in effect when a multitasking main executable program is encountered, the application will abend.

For a more detailed discussion of PL/I MTF support, see the IBM Enterprise PL/I for z/OS library. For more information about migration considerations for OS PL/I MTF applications, see the appropriate migration guide in the IBM Enterprise PL/I for z/OS library.