File Change Log File

FCL stores changes in a sparse file in the file system namespace. The FCL log file is always located in mount_point/lost+found/changelog. The FCL file behaves like a regular file, but some operations are prohibited. The standard system calls open(2), lseek(2), read(2) and close(2) can access the data in the FCL, while the write(2), mmap(2) and rename(2) calls are not allowed.

The FCL log file contains both the information about the FCL (stored in the FCL superblock), and the changes to files and directories in the file system, stored as FCL records. Details on the structure and semantics of the FCL superblock and FCL records, and the types of changes tracked by the FCL, are located in the header file /opt/VRTS/include/sys/fs/fcl.h (see File Change Log Programmatic Interface).