From Oracle FAQ
The Oracle Names Server is a server process that hands out TNS connect strings to clients. One can think of it as a central TNSNAMES.ORA server. Oracle Names enable clients to easily connect to a database without regard to specific physical locations or configurations on the network.
The Names Server is not available with Oracle 10g anymore and 10g clients (and higher versions) cannot use a Names Server to resolve connect strings. Users still using the names server should migrate to Oracle Internet Directory with LDAP directory naming.
Get running status:
$ namesctl status
Check if the names server resolve names:
$ namesctl query orcl \*
$ namesctl start
$ namesctl stop