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.
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.
Primary running on LparA and Shadow waiting on LparB.
Batch DBUTLTY with...
... and ...
//SYSIN DD *
As long as the MUF is active (ENABLED) on either lpar, the DBUTLTY job will run via XCF from the submitted lpar (/*JOBPARM SYSAFF=*).