Why 'fuser filename' command does not show PID when Oracle user executes it in home directory?

Issue

• When oracle user executes `fuser' on home directory:

testserver:(oracle) [user01] $ fuser *
test:                11312

• However, when root user executes the same command on Oracle user home directory:

[root@testserver user01]# pwd
/home/oradata/user01
[root@testserver user01]# fuser *
control01.ctl:       51250 51274 51280 51294 51963
essentel_idx_01.dbf: 51250 51274 51286
essentel_tbl_01.dbf: 51250 51274 51286
ic_idx_01.dbf:       51250 51256 51262 51268 51274 51286
ic_tbl_01.dbf:       51250 51256 51262 51268 51274 51286 51965
sysaux01.dbf:        51250 51256 51262 51268 51274 51286 51294
system01.dbf:         8193  8894  9141  9475  9724 51236 51250 51256 51262 51268 51274 51286 51288 51294 51963 51965 52129
temp01.dbf:          51250 51274 51286
test:                11312
undotbs01.dbf:        7999 51250 51256 51262 51268 51274 51286 51294 51300 51983
users01.dbf:         51250 51274 51286
[root@testserver user01]#

• Why is fuser not working correctly for the oracle account though many of the PIDs are owned by oracle?