SQL Server writes to the transaction log immediately, it writes the contents of modified data pages on checkpoints, but only for transactions that have committe

SQL Server writes to the transaction log immediately, it writes the contents of modified data pages on checkpoints, but only for transactions that have committed. For data pages that haven't been written to (dirty pages) when the system crashes, the recovery process can recreate completed transactional changes from the log (which is rolling forward), or wipes out failed transactions from the log (rolling backward).