I'm trying to get my head around how SQL Server handles the above. I understand that undo is held in the transaction log, but I'm just trying to figure out how the following scenario is handled:We have two users, user 1 and user 2 - both with READ COMMITTED isolation levels.User 1 updates a very large table (too big for the buffer), dirty pages start getting written to the datafiles.User 2 performs a select on the same table, on a row that has already been updated (but not committed)Where does SQL Server get the previous version of the row from? I assume it would be the undo in the transaction log? Is the above scenario even possible?
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