Actually, it would be better to have a subdirectory under /var/run (e.g. /var/run/ldap) that is owned by the LDAP user, and use that for argsfile/pidfile.

Yes later I did the same created /var/run/slapd directory and chown to ldap

This usually means that the user slapd is running as does not have permission to create new files, so ensure that that user owns your database directory (or log directory if you have configured via DB_CONFIG for them to be in another directory).

Thanks it has been resolved now.

Thanks. Askar