What caused the CA Datacom Shadow Multi-User (MUF) startup to terminate with error DB00205E - MULTI-USER ERROR - 1106 MUFPLEX NUMBER ALREADY IN USE?

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Issue/Introduction

What caused the CA Datacom Shadow Multi-User (MUF) startup to terminate with error

DB00205E - MULTI-USER ERROR - 1106 MUFPLEX NUMBER ALREADY IN USE? 

     1106 means: 

Data Sharing initialization failed due to specification of a number parameter on the MUFPLEX MUF startup option that is already in use for this instance of the MUFplex. 

Review MUF startup options and ensure that number is unique throughout the MUFplex. 

Environment

z/OSPrimary and Shadow Multi-User

Resolution

In this case, the Datacom MUF startup parameter SYSPLEX was missing the "S" value in the "mode" parameter which indicates that this is a Shadow MUF environment:

??? MUFPLEX ? name,number ?????????????? ,max_tasks ???????????????????????????

                           ?? ,locks ??              ?? ,mode ??

 ??????????????????????????????????????????????????????????????????????????????
   ?? ,tracesize ?? ?? ,mufplex_entry_ratio ??

 ???????????????????????????????????????????????????????????????????????????????
   ?? ,mufplex_element_ratio ??

 

 

In this case, the Shadow MUF successfully started after the MUF startup option ...

MUFPLEX name,*,,max_tasks 

... was corrected to add the ",S" ...

MUFPLEX name,*,,max_tasks,S 

 

Additional Information

Refer to CA Datacom® Core - 15.0 section on "MUFPLEX" 

https://docops.ca.com/ca-datacom/15-0/en/administrating/ca-datacom-db-database-and-system-administration/using-the-multi-user-facility/modifying-muf-startup-options/mufplex

•,mode (Optional) Establishes the choice of MUFplex operation relative to the mode of recovery.
. . .

• S
  To run in a Shadow MUF environment, specify an S as the mode for the MUFPLEX MUF startup option.
  For each physical MUF involved in the Shadow MUF environment, you should specify S for the MUFplex mode.
  A MUFPLEX mode of S is like a MUFPLEX mode of B in that no pipeline writes are done to the Coupling Facility.
  Implementation of mode S has only a small effect on how MUFPLEX modes A and B execute.
  For more information about running in a Shadow MUF environment, see Shadow MUF Environment.

Refer to CA Datacom® Messages for DB00205E and all other CA Datacom messages

https://docops.ca.com/ca-datacom-messages/en/ca-datacom-db-messages/processing-dbutlty-and-sql-messages/ca-datacom-db-processing-messages-db0xxxxc/db00205e