JES3 Resource Allocation
JES3 provides a device management facility called the main device scheduler (MDS) that can wholly or partially support the MVS™ allocation process. The purpose of MDS is to satisfy job resource requirements (the devices, volumes, and data sets needed) before and during job execution, thus allowing execution to proceed without allocation delays. MDS also allows controlled multisystem access to commonly accessible data sets in the loosely coupled environment.
You must choose whether to use the JES3 main device scheduler or use MVS (which
controls the job execution) for the entire allocation process as each step
begins execution. If you choose MDS, you must then decide whether utilization
of MDS is to be partial (set up some jobs, some resources) or total (set up
all jobs, all resources).
Note: You need to be aware that if
MDS is used to provide resource management, MDS takes into account the availability
of a job's scheduling environment during resource allocation. This scheduling
environment is a list of resource names and their required states that are
used to help ensure that units of work are sent to systems that have the appropriate
resources to handle them. Scheduling environments and resources are defined
by the installation in the WLM policy (see z/OS MVS Programming: Workload Management Services for more information).