How to remove a MIM system in a Virtual Control File (VCF) environment.

Document ID : KB000049829
Last Modified Date : 14/02/2018
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Description:

The MIM command REMOVE is not supported for permanently removing a MIM system in a VCF environment. A re-format of the MIM control file is required.

Solution:

MIM has long had a REMOVE command which permanently removes an inactive system from the MIMplex. This differs from the FREE command which is intended for a system which is currently inactive but will eventually rejoin the MIMplex.

However, when VCF support with CTCs was introduced some years ago, we were not able to support the REMOVE command for a VCF environment for various reasons. A MIM VCF environment is one in which CTCONLY, CTCDASD, or XCF is specified on the COMMUNICATION= keyword in the MIMINIT initialization member.

At this time, the only way to permanently remove a system from the MIMplex in a VCF environment is to perform a global shutdown of MIM, remove all of the settings in the MIMINIT member for the system, and then perform a format start of MIM on the first system where MIM is restarted. The first 2 steps can be reversed - update MIMINIT just before performing a global shutdown.

We do document in the MIM Statement and Command Reference that REMOVE is not supported for a VCF environment.

To maintain resource integrity, CA recommends that a global MIM shutdown only be done when all systems are being stopped prior to IPLs.

A format start of MIM (FORMAT=CF) clears out all of the old information in the MIM control file about a configuration and rebuilds the MIM configuration based on the settings in MIMINIT. On subsequent systems where MIM is started, you just perform a normal start (FORMAT=NONE). For customers who have MIM checkpoint files defined (required for CTCONLY and XCF communication methods), the procedure is to specify FORMAT=BOTH on the first system and then specify FORMAT=CHKPT on subsequent systems.

The settings in MIMINIT that must be changed or removed include DEFSYS, GLOBALVALUE, and CTCPATH statements.

The MIM team is discussing ways to make this process more flexible in the future.