This is the way I'm connecting to a Oracle Database:

my $database = 'TEST_DB';
my $DSN = "dbi:Oracle:$database";
my $dbh = DBI->connect( $DSN,
                          $DBUSER,
                          $DBPASS,
                          {AutoCommit => 1, RaiseError => 1}) or die "
+Can't connect DB [$!]";
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The content of the tnsnames.ora file is:

.../oracle/product/10.2.0/client_1/network/admin/tnsnames.ora

TEST_DB =
  (DESCRIPTION =
    (ADDRESS = (PROTOCOL = TCP)(Host = 192.168.1.1)(Port = 1526))
    (CONNECT_DATA =
      (SID = TESTDB)
    )
  )
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With the "sysdba" option '{ora_session_mode => ORA_SYSDBA}, i've got the following error, since that user doesn't have that privilege:

DBI connect('TEST_DB','user',...) failed: ORA-01031: insufficient priv
+ileges (DBD ERROR: OCISessionBegin)
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I hope it helps.

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