In usual work, the subscription has two_phase = on. I have to change this option at catchup stage only, but this parameter can not be altered. There was a patch proposal in past to implement altering of two_phase option, but it was rejected. I think, the recreation of the subscription with two_phase = off will not work.
The altering of two_phase was restricted because if there was a previously prepared transaction on the subscriber when the two_phase was on, and then it was turned off, the apply worker on the subscriber would re-apply the transaction a second time and this might result in an inconsistent replica.
Here's a patch that allows toggling two_phase option provided that there are no pending uncommitted prepared transactions on the subscriber for that subscription.
