If your using the cluster configuration repository (CCR) the use of tiebreaker disks can be enabled or disabled at any time by issuing an mmchconfig tiebreakerDisks command. The change will take effect immediately, and it is not necessary to shut down GPFS when making this change.
https://www.ibm.com/support/knowledgecenter/en/STXKQY_4.2.1/com.ibm.spectrum.scale.v4r21.doc/bl1ins_nodqtieb.htm
if your using server based repository I don't think we can do it while gpfs is active.
you can verify what repository your using with mmlscluster command.
#SpectrumScale#Support#SupportMigration