#1016 - Can't open file: './database_name/#sql-38f_36aa.frm' (errno: 24)

I have table in mysql with MyISAM storage engine. I want to create partition on a particular table, for this I am executing the query -

alter table Stops PARTITION BY KEY(`stop_id`) PARTITIONS 200

Where 'stop_id' is type of varchar. While executing the above query I am getting the error -

#1016 - Can't open file: './database_name/#sql-38f_36aa.frm' (errno: 24)

Can anybody please help me to resolve this problem?

Thank You.