reading entities as other writes to the database happen

Hi,

I have a requirement to read several unrelated entities. The relative state of the loaded entities should be as at a specific point in time i.e. the start of the read operation. Meanwhile other servers may be writing to the database and I don't wish to include any writes that occur after the read transaction has started.

So if I want to load entities A and B, but whilst I'm loading entity A someone else writes an update to entity B, when I move on to load entity B I wish to load the data prior to the update.



I think that using isolation levels is the way to go but am unclear on their use.