System definition removal from DEFSYS in MIMPLEX during DR

Products

• MIM Tape Sharing (MIA)
• MIM Data Sharing (MII)
• MIM Message Sharing (MIC)
• MIM Resource Sharing (MIM)

Issue/Introduction

We will be performing DR activity of one of our MIMplexes.

Over the the years, we have two systems which have been decommissioned, SYSA and SYSB. We did not remove the decommissioned systems from MIMPLEX on production since it required Global outage of MIM across the sysplex and outage of TAPE drives.

However, we want to know if we can delete the decommissioned system definition from DEFSYS for our MIMPLEX on DR systems ?

As of now no system in the DR site is active. MIMPLEX will be initialized at DR site when testing starts.

We will be using different MIMUNIT parm member for DR. So we have an option to delete the decommissioned system names from DEFSYS field. Is it feasible to do so ?

Currently, we have FORMAT=NONE in DR MIM PROC  and would like to keep this.

We are using DASDONLY with list structures.

We are not using CHECKPOINT files.

We use different coupling facility for DR as compared to production. All the structures are rebuilt when the first system comes up in DR.

We replicate the content of DASD but we don't have DASD control files for DR.

 

Environment

Release : 12.5

Component : MIM

Resolution

Our  Scenarios manual outlines all the places in the parms that need to be checked when a system is being decommissioned. 

If all that is left is to remove the old systems from the DEFSYS command, general guidance is 

• remove them from the DEFSYS in MIMINIT (as you already noted)
• bring up the first DR region with FORMAT=BOTH (checkpoint and control file)
• bring up all subsequent regions with FORMAT=CHKPT.

This will prevent any problems with synchronization between regions.

This is a unique scenario that is not included in our documentation.

Because MIM is running without Checkpoint files, and DR will be using new, empty list structures, those list structures will be filled with binary zeros.
In this case, MIM will automatically format the Control File even with FORMAT=NONE.
So changes to the DEFSYS can be made prior to bringing up the first MIM task on DR without any problems.