SQL & PL/SQL :: Format Data While Inserting Into Timestamp Field

I am trying to insert values in the timestamp field

system@id.world> create table t(t1 timestamp,t2 timestamp, t3 timestamp, t4 date);

Table created.

system@id.world> insert into t values(timestamp'2011-03-24 11:03:00.05','12-mar-2011 11.03.00.055',systimestamp,localtimestamp);

1 row created.

system@id.world> insert into t values(timestamp'2011-03-24 14:03:00.05','12-mar-2011 14.03.00.055',systimestamp,localtimestamp);

1 row created.

system@id.world> select t1 from t;

T1
---------------------------------------------------------------------------
24-MAR-11 11.03.00.050000
24-MAR-11 14.03.00.050000

system@id.world> select t2 from t;

T2
---------------------------------------------------------------------------
12-MAR-11 11.03.00.055000
12-MAR-11 14.03.00.055000

system@id.world> select t3 from t;

T3
---------------------------------------------------------------------------
24-MAR-11 11.29.04.491927
24-MAR-11 11.29.17.085396

system@id.world> select t4 from t;

T4
---------
24-MAR-11
24-MAR-11

system@id.world> select * from nls_instance_parameters;

PARAMETER VALUE
------------------------------ ----------------------------------------
NLS_LANGUAGE AMERICAN
NLS_TERRITORY AMERICA
NLS_SORT
NLS_DATE_LANGUAGE

[Code]...

PARAMETER VALUE
------------------------------ ----------------------------------------
NLS_TIME_TZ_FORMAT
NLS_TIMESTAMP_TZ_FORMAT
NLS_DUAL_CURRENCY
NLS_COMP
NLS_LENGTH_SEMANTICS BYTE
NLS_NCHAR_CONV_EXCP FALSE

17 rows selected.

system@id.world> select * from nls_database_parameters;

PARAMETER VALUE
------------------------------ ----------------------------------------
NLS_LANGUAGE AMERICAN
NLS_NCHAR_CHARACTERSET AL16UTF16
NLS_TERRITORY AMERICA
NLS_CURRENCY $

[Code]...

PARAMETER VALUE
------------------------------ ----------------------------------------
NLS_TIME_FORMAT HH.MI.SSXFF AM
NLS_TIMESTAMP_FORMAT DD-MON-RR HH.MI.SSXFF AM
NLS_TIME_TZ_FORMAT HH.MI.SSXFF AM TZR

[Code]...

20 rows selected.

system@id.world> show parameter nls_timestamp_fo

NAME TYPE VALUE
------------------------------------ ----------- ------------------------------
nls_timestamp_format string
system@id.world> create table newt(t1 timestamp);

Table created.

system@id.world> select localtimestamp from dual;

LOCALTIMESTAMP
---------------------------------------------------------------------------
24-MAR-11 11.31.07.667296

system@id.world> insert into newt values('12-jan-2010 11:00:00:068801');
insert into newt values('12-jan-2010 11:00:00:068801')
*
ERROR at line 1:
ORA-01830: date format picture ends before converting entire input string

system@id.world> insert into newt values('12-jan-2010 11.00.00.061');

1 row created.

system@id.world> insert into newt values('12-jan-2010 15.00.00.061');

1 row created.

system@id.world> select * from newt;

T1
---------------------------------------------------------------------------
12-JAN-10 11.00.00.061000
12-JAN-10 15.00.00.061000

system@id.world>

My questions are

1) what is significance of '.' here? insert into t values(timestamp'2011-03-24 11:03:00.05','12-mar-2011 11.03.00.055',systimestamp,localtimestamp);

2) while inserting using "values(timestamp'2011-03-24 11:03:00.05'" where this yyyy-mm-dd hh24:mi:ss.FF format comes from?

3)what is role of nls_timestamp_format of nls_database_parameters in this? how it allowed me to insert value "'12-mar-2011 14.03.00.055'" which has hh24 format?

4) Does the format of localtimestamp is decided by nls_database_parameters?

Note : I have not set nls_date_format in my session

I tried to read the link below but could not understand above

[URL]....