Extract timezone_region

Question

I am clearly missing something in handling timezones. I am inserting a timezone with the to_timestamp function but cannot extract it. Any ideas?
SQL> create table t (x date);
Table created
SQL> insert into t (x) values (to_timestamp_tz('9/12/2005 11:21 CST', 'MM/DD/YYYY HH12:MI TZR'));
1 row inserted
SQL> commit;
Commit complete
SQL> select extract(timezone_region from x) from t;
select extract(timezone_region from x) from t
ORA-30076: invalid extract field for extract source

Answer 1

$ oerr ora 30076
30076, 00000, "invalid extract field for extract source"
// *Cause: The extract source does not contain the specified extract field.
// *Action:
$ sqlplus test/test
SQL*Plus: Release 10.2.0.1.0 - Production on Mon May 1 18:09:22 2006
Copyright (c) 1982, 2005, Oracle.  All rights reserved.
Connected to:
Oracle Database 10g Enterprise Edition Release 10.2.0.1.0 - Production
With the Partitioning, OLAP and Data Mining options
TEST@db102 SQL> create table t (x timestamp with time zone);
Table created.
TEST@db102 SQL> insert into t (x) values (to_timestamp_tz('9/12/2005 11:21 CST', 'MM/DD/YYYY HH12:MI TZR'));
1 row created.
TEST@db102 SQL> select extract(timezone_region from x) from t;
EXTRACT(TIMEZONE_REGIONFROMX)
CST
TEST@db102 SQL>