We are trying to figure out which of the below statements is correct when talking about SQL Server mirroring:
The master database server executes the query, and takes the resulting transactions and ships them over to the secondary server, which "rolls in" the transactions into its database.
The master database server executes the query and simultaneously writes the query to the log. The log contents are sent to the slave and the queries are executed as they were on the primary.
Update: I unfortunately couldn't modify the two statements to avoid tampering. I think because the word "simultaneously" is used in the second statement it leads people away from the focus of question.
The main difference between the two statements is that in Statement 1, the transaction log that is sent to the secondary includes every row change action (insert/update/delete) that RESULTED from the query. In statement 2, the transaction log is actually only passing the query, and then executing it on the secondary. The key difference is, if Statement 2 is correct and you're updating millions of rows, it has little impact on how much data is passed (only the original query). However, if Statement 1 is correct, then updating millions of rows will require millions of rows of data to be sent to the secondary.