TNSping可以ping通
[oracle@racdg ~]$ tnsping racdg

TNS Ping Utility for Linux: Version 11.2.0.4.0 - Production on 11-MAR-2020 00:58:35

Copyright © 1997, 2013, Oracle. All rights reserved.

Used parameter files:

Used TNSNAMES adapter to resolve the alias
Attempting to contact (DESCRIPTION = (ADDRESS = (PROTOCOL = TCP)(HOST = scan-cluster)(PORT = 1521)) (CONNECT_DATA = (SERVER = DEDICATED) (SERVICE_NAME = racdg) (UR = A)))
OK (10 msec)

TNS登陆却报错
sqlplus sys/123456@orcldg as sysdba

SQL*Plus: Release 11.2.0.4.0 Production on Wed Mar 11 00:54:19 2020

Copyright © 1982, 2013, Oracle. All rights reserved.

ERROR:
ORA-12154: TNS:could not resolve the connect identifier specified

TNS的配置：
racdg =
(DESCRIPTION =
(ADDRESS = (PROTOCOL = TCP)(HOST = scan-cluster)(PORT = 1521))
(CONNECT_DATA =
(SERVER = DEDICATED)
(SERVICE_NAME = racdg)
(UR = A)
)

)

请问大佬们，这是什么情况？