Subsystem early code - EQQINITP

Each z/OS subsystem builds a subsystem vector table (SSVT) control block that defines what functions are supported by that subsystem. The IBM Z Workload Scheduler SSVT is built by a separate module, EQQINITP, which is invoked during the master scheduler initialization at IPL. EQQINITP does the following:
  • Sets the UPSS bit in the (SSVT) so that IBM Z Workload Scheduler can be started under JES
  • Builds common storage area (CSA) control blocks to queue events until IBM Z Workload Scheduler is started
  • Builds a subsystem extension (SSX) block and chains it to the SSVT
  • Builds an SSVT and chains it to the subsystem communication vector table (SSCVT).
The SSVT that EQQINITP builds specifies that IBM Z Workload Scheduler supports two subsystem calls:
  • A request for service from an IBM Z Workload Scheduler dialog (type 67)
  • A notification about a tracking event (type 68).

The code that is required to support these two subsystem calls is contained in a separate load module, EQQSSCMP . This module is loaded in ECSA by EQQINITP processing at IPL. It can be temporarily replaced when the IBM Z Workload Scheduler address space is started using the SSCMNAME keyword of OPCOPTS, see Customization and Tuning.