High Quality Content by WIKIPEDIA articles! Common Log File System (CLFS) is a general-purpose logging subsystem that is accessible to both kernel-mode as well as user-mode applications for building high-performance transaction logs. It was introduced with Windows Server 2003 R2 and included in later Windows OSs. CLFS can be used for both data logging as well as for event logging. CLFS is used by TxF and TxR to store transactional state changes before they commit a transaction.