When WSAT Subordinate Coordinator handles a commitVolatile or a rollbackVolatile call it assumes that a commit or rollback of its durable participants has already happened and hence that the relevant outcome has been stored in the transaction (basic action) field finalStatus. This is used to parameterise a call to afterCompletion, thereby notifying any local heuristic outcome. However, if the preceding prepare call returned READ_ONLY then commitVolatile or rollbackVolatile are called without an intervening call to commit or rollback and finalStatus will not be valid. This special case needs to be detected and recorded at prepare so that commitVolatile and rollbackVolatile can hardwire call the values COMMITTED or ABORTED.