confluence indexs files question

[Anderson Hsu]

Dear all, 

Why I can not find all index files at the path of /var/confluence/index/plugin/usage? Sometimes it's have 13 files, but sometimes it became 12 or 11 files. Detail is listed as below:

-23*92.fdt

-23*92.fdx

-23*92.fnm

-23*92.frq

-23*92.nrm

-23*92.prx

-23*92.tii

-23*92.fis

-23y6f.cfs

-23y6g.cfs

-23y6h.cfs

segments_lkz.p0

segments.gen

The -23y6g.cfs, -23y6h.cfs sometimes is disappear.