Comment 2 for bug 1080914

Chance are this will never work. MyISAM support for PXC isn't a priority afaik. Even if it were, it would still be risky for pt-osc (very difficult to say how non-transactional stuff works in a semi-sync cluster with 3 tables, 3 triggers, other writers, etc.). We've already noted in the pt-osc docs that,

"""
pt-online-schema-change works with Percona XtraDB Cluster (PXC) 5.5.28-23.7
and newer, but there are two limitations: only InnoDB tables can be altered,
and C<wsrep_OSU_method> must be set to C<TOI> (total order isolation).
"""

So I'm just going to say that this is now "policy" and close this bug.