You found this messages if you try to remove to many file in a directory, try this solution :
find . -name '*' | xargs rm
or if you want delete spesific file name, for example you want delete file with sess_ from the begining try this command :
find . -name 'sess_*' | xargs rm
Another solution use bash loop scripts, fir example :
for i in 'seq 0-9'a b c d e f g h i j k l m n o p q r s t u v w x y z ; do rm $i* ; done