it refers to free innodb tablespace.
From: "Rozeboom, Kay [DAS]" <KAY.ROZEBOOM@stripped>
To: "mysql@stripped" <mysql@stripped>
Sent: Thursday, November 10, 2011 10:03 AM
Subject: "InnoDB free" - What does it really mean?
In the "show table status" output, there is comment field labeled "InnoDB free". Can
someone explain what kind of free space is counted in this figure? Is it space that
is not currently part of any segment? Does it include empty pages within
segments? Does it include unused space within pages?
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