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Building a Single Control Block Structure z/OS DFSMS Using Data Sets SC23-6855-00 |
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To share successfully within a task or between subtasks, you should
ensure that VSAM builds a single control block structure for the data
set. This control block structure includes blocks for control information
and input/output buffers. All subtasks access the data set through
this single control block structure, independent of the SHAREOPTION
or DISP specifications. The three methods of achieving a single control
block structure for a VSAM data set while processing multiple concurrent
requests are:
Multiple ACBs must be in the same address space, and they must be opening to the same base cluster. The connection occurs independently of the path selected to the base cluster. If the ATTACH macro is used to create a new task that will be processing a shared data set, let the ATTACH keyword SZERO to default to YES or code SZERO=YES. This causes subpool 0 to be shared with the subtasks. For more information about the ATTACH macro see z/OS MVS Programming: Authorized Assembler Services Reference ALE-DYN. This also applies to when you are sharing one ACB in a task or different subtasks. To ensure correct processing in the shared environment, all VSAM requests should be issued in the same key as the job step TCB key. |
Copyright IBM Corporation 1990, 2014
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