对于不同的ORACLE连接串，可能需要调整连接方式,都需要有ORACLE客户端：

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1. dwapprac =
???? (DESCRIPTION =
???? (ADDRESS = (PROTOCOL = TCP)(HOST = 10.125.60.25)(PORT = 1521))
???? (ADDRESS = (PROTOCOL = TCP)(HOST = 10.125.60.26)(PORT = 1521))
???? (LOAD_BALANCE = yes)
???? (CONNECT_DATA =
?????? (SERVER = DEDICATED)
?????? (SERVICE_NAME = dwapprac)
?????? (FAILOVER_MODE =
???????? (TYPE = SELECT)
???????? (METHOD = BASIC)
???????? (RETRIES = 180)
???????? (DELAY = 5)
?????? )
???? )
?? )

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my $db_url="dbi:Oracle:$database_name";
                my $dbh = DBI->connect($db_url,$db_user,$db_password
                                ,{AutoCommit => 1
                                ,RaiseError => 0
                                ,PrintError => 0}
                               ) or printf STDERR "$DBI::err ($DBI::errstr)\n";
                unless ( defined($dbh) ) { return undef; }
                return ($db_type,$dbh);

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2. dwapp =
? (DESCRIPTION =
??? (LOAD_BALANCE=NO)
??? (ADDRESS_LIST =
????? (ADDRESS = (PROTOCOL = TCP)(HOST = 10.125.70.54)(PORT = 1522))
????? (ADDRESS = (PROTOCOL = TCP)(HOST = 10.125.70.55)(PORT = 1522))
??? )
??? (CONNECT_DATA =
????? (SERVICE_NAME = dwapp)
??? )
? )

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my $db_url="dbi:Oracle:host=$host;sid=$database_name;port=$port";
                my $dbh = DBI->connect($db_url,$db_user,$db_password
                                ,{AutoCommit => 1
                                ,RaiseError => 0
                                ,PrintError => 0}
                               ) or printf STDERR "$DBI::err ($DBI::errstr)\n";
                unless ( defined($dbh) ) { return undef; }
                return ($db_type,$dbh);

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