Berkeley DB

Transaction Limits

Transactions are identified uniquely by 32-bit unsigned integers. The high-order bit of the transaction ID is reserved (and defined to be 1), resulting in just over two billion unique transaction IDs. Each time that recovery is run, the beginning transaction ID is reset with new transactions being numbered, starting from 1. This means that recovery must be run at least once every two billion transactions.

It is possible that some environments may need to be aware of this limitation. Consider an application performing 600 transactions a second for 15 hours a day. The transaction ID space will run out in roughly 66 days:

2^31 / (600 * 15 * 60 * 60) = 66 

Doing only 100 transactions a second exhausts the transaction ID space ...