Guaranteed commit outcome in a distributed transaction processing system

Techniques described herein distinguished between global transactions in a session managed by a transaction manager, and those in the same session that are managed by the resource manager using the optimizations. The techniques provide a guaranteed commit outcome when the commit is managed by the resource manager, or when a transaction manager is managing the transaction. Switching between the different techniques to provide a guaranteed outcome occurs in a safe, performing, and silent manner, based on who controls the current transaction in a session. The solution includes one-phase processing, read only optimizations, and promotable transactions.