#Generated tnsnames.ora by gen_tnsnames.sh script
#Localnode service connectivity 
ABCD12.COMPANYDOMAIN.COM = 
  (DESCRIPTION = 
    (ADDRESS_LIST = 
      (ADDRESS = (PROTOCOL = TCP)(HOST = testserver24.companydomain.com )(PORT = 30710)) 
    )
    (CONNECT_DATA = 
      (INSTANCE_NAME = ABCD12) 
      (SERVICE_NAME = ABCD12.COMPANYDOMAIN.COM) 
    )
  )

##</code><code>##

use DBI;
use DBD::Oracle qw(:ora_session_modes);

my $dsn = "dbi:Oracle:";
#$ENV{ORACLE_SID} = "ABCD12";
$ENV{ORACLE_SID} = "ABCD12.COMPANYDOMAIN.COM";
delete $ENV{TWO_TASK};
my $dbh = DBI->connect($dsn, "", "", { ora_session_mode => ORA_SYSDBA });

##</code><code>##

DBI connect('','',...) failed: ORA-12545: Connect failed because target host or object does not exist (DBD ERROR: OCIServerAttach)