Failed to su to user

I am unable to su to functional user, though changed the soft-hard limit for open files in limits.conf.
The following command did not help.

ulimit -n <value>

While su to user, the error I am getting is -

su: cannot set user id: Resource temporarily unavailable

Whether I need to restart the application to get the limit effected for the functional user ?

Please help

Hello atanubanerji,

This issue can happen if the user's process-run-limit is reached. The process limit can be increased by editing: /etc/security/limits.conf file with a user having root permission. The entry to check will be similar to, an example:

 *          hard     nproc         100
 

No need to restart any services.

Thanks,
R. Singh