What are the benefits of CA MIM Early Start Mechanism
Document ID : KB000126691
Last Modified Date : 13/02/2019
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Introduction:
We received a document in which CA-MIM Early start mechanism was one of the recommendations to activate on our customer systems. On each LPAR where we use MIM, it is started via COMMAND member, and it is started before JES2.
Question:
Can you describe the benefits of implementing the CA MIM for z/OS Early Start Mechanism?
Answer:
  1. Running with the CA MIM Early Start Mechanism ensures that CA MII synchronization occurs early in the IPL process so all RESERVE and SYSTEMS ENQ requests are suspended to avoid unconverted reserves, deadly embraces, and/or integrity exposures. Use the CA MIM for z/OS Early Start mechanism to prevent these issues. The Early Start Mechanism uses SYS1.PARMLIB to install and execute the module MIMESNQX early in the IPL process. MIMESNQX internally starts the CAMIMGR address space to start monitoring global resources. All RESERVE and SYSTEMS ENQ requests are suspended until the CAMIMGR address space is fully initialized.
  2. As a general practice, service providers should execute with a higher dispatching priority than service requestors. CA MIM for z/OS provides vital system services for z/OS address spaces and users. Therefore, CA MIM for z/OS must obtain the resources necessary to provide a time critical service. Utilizing the Early Start Mechanism allows the CA MIM for z/OS address space to run as a system created address space to provide optimal throughput. System address spaces execute with a fixed dispatching priority of 255.
Additional Information:
Some related areas as found in the documentation for the current release:  If you are running with heavy managed enqueue activity, you will benefit by having the CA MII address space run as a system service address space. The CA MIM Address Space Creation Utility does not provide much benefit for CA MIM address spaces running only the CA MIA or CA MIC components. Therefore, you may want to employ the CA MIM Address Creation Utility for your CA MII task, but choose not to use it for your CA MIM Tape or Console management tasks.