There is no concern running a DEFRAG to a primary MUF that has a Shadow MUF in waiting
Given startup option: MUFPLEX
plexname,*,,250,
S The MUFPLEX mode
'S' confirms that no structure CF coupling facility is being used.
As per documentation on MUFPLEX and mode 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.
https://docops.ca.com/ca-datacom/15-1/en/administrating/ca-datacom-db-database-and-system-administration/using-the-multi-user-facility/modifying-muf-startup-options/mufplex "The concern would be if a true multi-MUF environment was set up and using a CF structure with a different mode.
DBUTLTY DEFRAG can be run from any lpar that has access to the active MUF via XCF.
Example:
Primary running on LparA and Shadow waiting on LparB.
Batch DBUTLTY with...
/*JOBPARM SYSAFF=*
... and ...
//SYSIN DD *
DEFRAG DBID=
dbid /*
As long as the MUF is active (ENABLED) on either lpar, the DBUTLTY job will run via XCF from the submitted lpar (/*JOBPARM SYSAFF=*).