This is the documentation for CDH 4.6.0.
Documentation for other versions is available at Cloudera Documentation.
The File Channel serialization format changed in the CDH 4.1.0 release of Flume. If you are using the File Channel in a Flume deployment from CDH 4.0, you must first empty the channel, shut down the Agent and delete any channel specific files, upgrade and restart the Agent in order to reinitialize the channel with the correct format. Alternatively you could shutdown the Agent, move the File Channel files to a staging area, upgrade the Agent and restart. The File Channel files in the staging area can then be replayed by a Flume installation of prior version asynchronously. The File Channel was marked as experimental in CDH 4.0.