ABCs of z/OS System Programming Volume 13

Main device scheduling (MDS)

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 JES3 complex environment.

You must choose whether to use the JES3 main device scheduler ...