上面的sqlnet.ora文件說明：
SQLNET.AUTHENTICATION_SERVICES= (NTS)——這個表示采用os認證，在數(shù)據(jù)庫服務(wù)器上，可以利用sqlplus “/ as sysdba”。一般這個配置在windows上是ok的，在unix環(huán)境下可能會有問題，一般在unix下可以去掉這個配置。
NAMES.DIRECTORY_PATH= (TNSNAMES, HOSTNAME, ONAMES)——表示將首先利用tnsnames進行解析；如果tnsnames解析不到，將使用hostname解析；如果hostname解析不 到，將采用onames進行解析。
被注釋掉的NAMES.DEFAULT_DOMAIN = us.oracle.com——表示采用默認的domain name為us.oracle.com，在tnsnames.ora中如果配置對應(yīng)的解析，如果原來的別名oralocal，那么，當啟用這個參數(shù)后，在 tnsnames中的配置要改成oralocal.us.oracle.com。在使用tnsping時或者sqlplus登錄時，只需寫前面的別名，系 統(tǒng)會自動加上后面的domain name來進行解析。
檢查完畢sqlnet.ora，一般都會發(fā)現(xiàn)是使用tnsname來解析別名的，那么，tnsnames.ora中可以有哪些配置種類呢？
# TNSNAMES.ORA Network Configuration File: $ORACLE_HOME/NETWORK/ADMIN/tnsnames.ora
# Generated by Oracle configuration tools.
###### 一般的配置 ##################################
ORALOCAL =
(DESCRIPTION =
(ADDRESS_LIST =
(ADDRESS = (PROTOCOL = TCP)(HOST = 127.0.0.1)(PORT = 1521))
)
(CONNECT_DATA =
(SERVER = DEDICATED)
(SERVICE_NAME = oralocal)
)
)
###### 這樣也行，用SID=oralocal ###########################
ORALOCAL_2 =
(DESCRIPTION =
(ADDRESS_LIST =
(ADDRESS = (PROTOCOL = TCP)(HOST = 127.0.0.1)(PORT = 1521))
)
(CONNECT_DATA =
(SERVER = DEDICATED)
(SID = oralocal)
)
###### RAC的配置(3節(jié)點rac) ###############################
ORALOCAL =
(DESCRIPTION =
(load_balance = yes)
(failover = on)
(ADDRESS_LIST =
(ADDRESS = (PROTOCOL = TCP)(HOST = 192.168.1.1)(PORT = 1521))
(ADDRESS = (PROTOCOL = TCP)(HOST = 192.168.1.2)(PORT = 1521))
(ADDRESS = (PROTOCOL = TCP)(HOST = 192.168.1.3)(PORT = 1521))
)
(CONNECT_DATA =
(SERVICE_NAME = oralocal)
(SERVER = DEDICATED)
(failover_mode=(type=select)(method=basic)(retries=20)(delay=20))
)
)
ORALOCAL_NODE1 =
(DESCRIPTION =
(ADDRESS_LIST =
(ADDRESS = (PROTOCOL = TCP)(HOST = 192.168.1.1)(PORT = 1521))
)
(CONNECT_DATA =
(SERVICE_NAME = oralocal)
(INSTANCE_NAME = oralocal_node1)
)
)
ORALOCAL_NODE2=
(DESCRIPTION =
(ADDRESS_LIST =
(ADDRESS = (PROTOCOL = TCP)(HOST = 192.168.1.2)(PORT = 1521))
)
(CONNECT_DATA =
(SERVICE_NAME = oralocal)
(INSTANCE_NAME = oralocal_node2)
)
)
ORALOCAL_NODE3 =
(DESCRIPTION =
(ADDRESS_LIST =
(ADDRESS = (PROTOCOL = TCP)(HOST = 192.168.1.3)(PORT = 1521))
)
(CONNECT_DATA =
(SERVICE_NAME = oralocal)
(INSTANCE_NAME = oralocal_node3)
)
)
)
###### DATA GUARD配置（primary庫和standby庫都需要配置）##############
standby =
(DESCRIPTION =
(ADDRESS_LIST =
(ADDRESS = (PROTOCOL = TCP)(HOST = 192.168.2.2)(PORT = 1521))
)
(CONNECT_DATA =
(SERVER=DEDICATED)
(SERVICE_NAME = oralocal)
)
)
primary =
(DESCRIPTION =
(ADDRESS_LIST =
(ADDRESS = (PROTOCOL = TCP)(HOST = 192.168.2.1)(PORT = 1521))
)
(CONNECT_DATA =
(SERVER=DEDICATED)
(SERVICE_NAME = oralocal)
)
)
另外需要注意的2點情況：
（1）如果tnsnames中的service_name配置錯誤，配置成了instance_name了，這個時候會發(fā)生tnsping能通，但是 sqlplus連接不上的奇怪情況。報錯ORA-12514: TNS:listener could not resolve SERVICE_NAME given in connect descriptor。這個時候查錯的時候，需要檢查對應(yīng)的service_name。
（2）如果遠程數(shù)據(jù)庫是rac，而且本地客戶端端遠程數(shù)據(jù)庫處于不同的網(wǎng)段，通過公網(wǎng)鏈接，rac對外的ip映射只有一個，即只映射到一個節(jié)點。請注意在 客戶端配置tnsnames的時候按照單機的情況來配置。呵呵，dba不僅僅要學(xué)習(xí)oracle，了解一些網(wǎng)絡(luò)的知識，特別是自己系統(tǒng)的網(wǎng)絡(luò)架構(gòu)，也是需 要的。