As long as you have acquired the needed database space there is no real limit.
But I would not recommend having as large journal as this because it will take a very long time to post them, and if there are an error in your journal it will take a long time to roll back the posting.
So I would recommend you split it in to smaler chucks and process posting in smaller batch.
Typically I would not have more than around 10000-15000 lines in a journal before i posted it. And I would really aim for lower numbers if i could.
When it comes to posted transactions I would not worry about the number of records. The system is able to handle lots of transaction, but you have to chose a good approach if you have a lot of lines you need to post.
