Starting a functional subsystem
A functional subsystem (FSS) is a set of routines that performs work that can be offloaded from the JES3 global address space. An FSS runs in an FSS address space, which can be located on the global or a local. By off-loading some of the JES3 workload, virtual storage space might be freed in the JES3 global address space.
The events causing JES3 to start a functional subsystem differ for the particular type of FSS, either a writer FSS or a C/I FSS.
An output writer FSS, which supports
specific printer devices, is started by JES3 in response to one of
the following:
- A *CALL,WTR,OUT=device command is entered that specifies an output device controlled by an FSS (hot writer).
- An output device controlled by an FSS becomes available and there is eligible work (dynamic writer).
A converter/interpreter FSS is started
automatically by JES3 in response to one of the following:
- JES3 is initiated on a main having a C/I FSS with automatic starting (START=YES) and that main is connected to the global. The START= keyword is located on the FSSDEF initialization statement.
- A *MODIFY,F,FSS=fssname,ST=Y command is entered for a C/I FSS, changing the start value from NO to YES. (DSP counts are greater than 0.)
- A *MODIFY,F,FSS=fssname,DSPC=(mmm,nnn) command is entered for a C/I FSS, changing a DSP count value from zero. (Start value must be YES.)
- A *MODIFY,F,FSS=fssname,SYS= command is entered for a C/I FSS, changing the main on which the FSS is assigned to another main which is active.