"The DEFERRABLE transaction property has no effect unless the transaction is also SERIALIZABLE and READ ONLY. When all three of these properties are selected for a transaction, the transaction may block when first acquiring its snapshot, after which it is able to run without the normal overhead of a SERIALIZABLE transaction and without any risk of contributing to or being canceled by a serialization failure. This mode is well suited for long-running reports or backups."
Could anyone expound on the above? What are the real life differences between the two commands below? Would this be applicable at all to sessions on a physical replica?
SET SESSION CHARACTERISTICS AS TRANSACTION ISOLATION LEVEL SERIALIZABLE READ ONLY DEFERRABLE;
SET SESSION CHARACTERISTICS AS TRANSACTION READ ONLY;
