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## JES3/DFSMS processing 

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DFSMS is called by the z/OS interpreter to perform these functions: 

GLYPH<SM590000> Update the scheduler work area (SWA) for DFSMS tape requests. 

GLYPH<SM590000> Call ACS exits for construct defaults. 

DFSMS system-managed tape devices are not selected by using the UNIT parameter in the JCL. For each data definition ( DD ) request requiring a TS3500 tape library unit, a list of device pool names is passed, and from that list, an LDG name is assigned to the DD request. This results in an LDG name passed to JES3 MDS for that request. Device pool names are never known externally. 

