LISTENER =

(ADDRESS_LIST=

(ADDRESS=(PROTOCOL=tcp)(HOST=jlb4101-PC)(PORT=1521))

(ADDRESS=(PROTOCOL=ipc)(KEY=PNPKEY)))

tnsnames.ora里面是

IP78.FLOW_dev=
(DESCRIPTION =
(ADDRESS = (PROTOCOL = TCP)(HOST = 192.168.0.78)(PORT = 1521))
(CONNECT_DATA =
(SERVER = DEDICATED)
(SERVICE_NAME = pdborcl)
)
)
flow_test_IP78PDB=
(DESCRIPTION =
(ADDRESS = (PROTOCOL = TCP)(HOST = 192.168.0.78)(PORT = 1521))
(CONNECT_DATA =
(SERVER = DEDICATED)
(SERVICE_NAME = pdborcl)
)
)

错误是

登陆 plsql会有上图所示的连接标识符，检查一下自己的配置文件中是否配置了这个连接标识符。
例如：
配置文件的参照目录结构（也就是本机数据库的安装目录），
E:\oracle\ora92\network\ADMIN\tnsnames.ora
参照配置，
GBK_10.137.165.224 =
(DESCRIPTION =
(ADDRESS_LIST =
(ADDRESS = (PROTOCOL = TCP)(HOST = 10.137.165.224)(PORT = 1521))
)
(CONNECT_DATA =
(SERVICE_NAME = GBK)
)
)