What Is a READ ONLY Transaction?

A READ ONLY transaction is a transaction in which the read consistency is set at the transaction
level. In a READ ONLY transaction, a logical snapshot of the database is created at the beginning
of the transaction and released at the end of the transaction. This guaranties that all reads in all
statements within this transaction get consistent data from the database.
For example, if you have a transaction with many statements that takes 10 hours to be executed,
a snapshot of the database will be created for this transaction for 10 hours. If a query statement is
executed at the beginning of the transaction and at the end of the transaction, it will return the
same result guarantied. In another word, data changes made during this 10 hours by other users
will not impact the execution of statements within this transaction.