I'm using AlwaysOn synchronous replica. User issues an update on primary via SSMS. In order for the transaction to be committed on primary, the tran needs to get to the secondary, be hardened to the secondary log & an ack sent & received back. Let's say this takes 50 ms. Does this mean the user sits and waits for 50 ms for a response back to his SSMS window?
What happens when the secondary is unavailable for an hour? Does he now sit and wait for the hour?
I'm clearly not getting what effect the actual tran delay is having to the user. I'd be super grateful for clarification.
Unless there was some sort of maintenance occurring, why would the secondary be offline for an hour? Or was this just a scenario you were using as an example?
The answer is no, the user will not be sitting there waiting for an hour. If the secondary is unavailable, such as it being shut down, the transactions that need to be committed on the secondary will simply wait until it is available. Your transaction logs will probably start growing.
If in fact this is simply a matter of latency between the primary and secondary, you will definitely wait until the transaction is committed on the secondary.