partition out of resources

[Yang HuanWei]

I got an error message when too many program are running at the same time.

Error Description: Out of resources when opening
file '.\data\cntxt_hist#P#cntxt_hist_p30.MYD' (Errcode: 24)

I didn't get this error before I altered table to 30 partitions, so I wonder
if mysql opened all partition files for each program accessing(SQL query).
The open_file_limit setting of mysql is 500.
Currently, I tried to enlarge the open_file_limit setting to 2000. But it is
not the long-term solution for allowed connection > 100.

Have any solution to solve this error?
or if I know which partition be queried in my SQL, can I limit mysql to open
this specific partition file using SQL statement?