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By default, FCL logging is deactivated and can be activated on a per file system basis using the fcladm command.
See the fcladm(1M) manual page.
When the FCL is activated, new FCL records are appended to the FCL file as the file system changes occur. When the FCL is turned off, further recording stops, but the FCL file remains at the lost+found/changelog. You can only remove an FCL file by using the fcladm rm command.
The FCL has an associated version that represents the layout or the internal representation of the FCL, along with the list of events recorded in the FCL. Whenever a new version of VxFS is released, the following occurs:
This results in the FCL version getting updated. For instance, in VxFS 4.1, the default was Version 3. In Vxfs 5.0, the default is Version 4. FCL Version 4 records additional sets of events that are not available in Version 3 (such as file opens). To provide backward compatibility for applications developed on VxFS 4.1, VxFS 5.0 provides an option to specify an FCL version (either 3 or 4) during activation. Depending on the specified version, the logging of the new record types is either allowed or disallowed.
The logging of most of the newly added records in VxFS 5.0 (for example, file opens, I/O statistics etc.) is optional and is turned off by default. Recording of these events can be enabled or disabled using the set|clear options of the fcladm command.
The FCL meta-information comprising the file system state, version, and the set of events being tracked is persistent across reboots and file system unmounts or mounts. The version and event information is also persistent across re-activations of the FCL.