MySQL 5.7 Reference Manual Including MySQL NDB Cluster 7.5 and NDB Cluster 7.6
The file_instances table lists
all the files seen by the Performance Schema when executing
file I/O instrumentation. If a file on disk has never been
opened, it is not in
file_instances. When a file is
deleted from the disk, it is also removed from the
file_instances table.
The file_instances table has
these columns:
FILE_NAME
The file name.
EVENT_NAME
The instrument name associated with the file.
OPEN_COUNT
The count of open handles on the file. If a file was
opened and then closed, it was opened 1 time, but
OPEN_COUNT is 0. To list all the files
currently opened by the server, use WHERE
OPEN_COUNT > 0.
TRUNCATE TABLE is not permitted
for the file_instances table.