Displays the values of the dynamically memory pools.

COLUMN name FORMAT A40
COLUMN value FORMAT A40

SELECT name,
value
FROM v$parameter
WHERE SUBSTR(name, 1, 1) = '_'
ORDER BY name;

COLUMN FORMAT DEFAULT

Displays high water mark statistics.

COLUMN name FORMAT A40
COLUMN highwater FORMAT 999999999999
COLUMN last_value FORMAT 999999999999
SET PAGESIZE 24

SELECT hwm1.name,
hwm1.highwater,
hwm1.last_value
FROM dba_high_water_mark_statistics hwm1
WHERE hwm1.version = (SELECT MAX(hwm2.version)
FROM dba_high_water_mark_statistics hwm2
WHERE hwm2.name = hwm1.name)
ORDER BY hwm1.name;

COLUMN FORMAT DEFAULT

Displays information on the current wait states for all active database sessions.

SET LINESIZE 250
SET PAGESIZE 1000

COLUMN username FORMAT A15
COLUMN osuser FORMAT A15
COLUMN sid FORMAT 99999
COLUMN serial# FORMAT 9999999
COLUMN wait_class FORMAT A15
COLUMN state FORMAT A19
COLUMN logon_time FORMAT A20

SELECT NVL(a.username, '(oracle)') AS username,
a.osuser,
a.sid,
a.serial#,
d.spid AS process_id,
a.wait_class,
a.seconds_in_wait,
a.state,
a.blocking_session,
a.blocking_session_status,
a.module,
TO_CHAR(a.logon_Time,'DD-MON-YYYY HH24:MI:SS') AS logon_time
FROM v$session a,
v$process d
WHERE a.paddr = d.addr
AND a.status = 'ACTIVE'
ORDER BY 1,2;

SET PAGESIZE 14

Different ways to set up NLS parameters

The word NLS means National Language Support. The NLS_* parameters determine the
locale-specific behavior on both the client and the server; where * of NLS_* is for various strings which make various NLS parameters.

There are many NLS_* parameters like NLS_SORT, NLS_LANGUAGE, NLS_CHARACTERSET, NLS_DATE_LANGUAGE etc. In this post I will show how the NLS parameters can be set based on their setting of priority.

1)In SQL functions:
If you set NLS_* parameters inside SQL functions then that setting has the highest priority.

You can set in SQL functions like,
TO_CHAR(sysdate, 'DD/MON/YYYY', 'nls_date_language = FRENCH')

Below is an example. Note that in my client machine FRENCH language is not installed so it might not display properly.


SQL> select sysdate from dual;

SYSDATE
---------
07-FEB-09

SQL> select TO_CHAR(sysdate, 'DD/MON/YYYY', 'nls_date_language = FRENCH') from dual;

TO_CHAR(SYSDA
-------------
07/FEB./2009


Setting in this way (inside sql functions) overrides the default values that are set for the session in the initialization parameter file, set for the client with environment variables, or set for the session by the ALTER SESSION statement.

2)With the ALTER SESSION statement:
Setting through ALTER SESSION parameter has the second highest priority. Setting by an ALTER SESSION statement override the default values that are set for the session in the initialization parameter file or set by the client with environment variables.

Below is an example. As in my client machine Japanese language is not installed so displaying in Japanese character might not work properly.


SQL> select sysdate from dual;

SYSDATE
---------
07-FEB-09

SQL> alter session set NLS_DATE_LANGUAGE=JAPANESE;

Session altered.

SQL> select sysdate from dual;

SYSDATE
----------
07-02 -09


3)Through Environmental variable on the client machine:
This setting has the third highest priority. Through OS environmental variable you can set NLS_* parameters. Setting of environmental variable is platform specific. On windows machine you can set by,
C:>set NLS_*=value;
On unix machine
$export NLS_*=value (bash shell)
$setenv NLS_*=value (c shell)

Below is an example on my windows client machine.
C:\>set NLS_SORT=FRENCH

4)As initialization parameters on the server:
You can set the NLS_* parameters in the server machine inside the initialization parameter file. Setting in the initialization parameter specify a default session NLS environment. Setting in this way has no effect on the client side, they control only the server's behavior.
For example, if you use spfile then you can set NLS_TERRITORY parameter by below,

SQL> ALTER SYSTEM SET NLS_TERRITORY = "CZECH REPUBLIC" scope=spfile;

System altered.
Then in order to effect bounce database.

If I draw a table based on priority and ways to do then it will be like,


Priority Ways to do the task.
----------- -----------------------------------------
1 (highest) Set in SQL functions
2 Set by an ALTER SESSION statement
3 Set as an environment variable
4 Specified in the initialization parameter file
5 (lowest) Default

Related Documents
Unicode characterset in Oracle database.
What is NLS_LANG environmental variable?
What is database character set and how to check it
What is national character set / NLS_NCHAR_CHARACTERSET?
Which datatypes use the National Character Set?
What is character set and character set encoding

What is character set and character set encoding

The term character set indicates the set of characters used by a particular encoding system. It does not represent the numeric assignments of the characters nor the order of the characters but just the set of characters under an encoding system.

The term character set encoding refers how each character of a character set is represented under an encoding system. In order words character set encoding is the mapping of characters to binary values. It pairs the character from the character set with a natural number. Suppose, in 8-bit character set encoding each character from the character set is mapped to the values range from 0-255.

For example capital A will be encoded to 65. Every time you press A from keyboard it will be interpreted as 65. This system also named as encoding scheme.

Related Documents
Unicode characterset in Oracle database.
What is NLS_LANG environmental variable?
What is database character set and how to check it
Different ways to set up NLS parameters
What is national character set / NLS_NCHAR_CHARACTERSET?
Which datatypes use the National Character Set?

Which datatypes use the National Character Set?

There are three datatypes which can store data in the national character set.

1)NCHAR: It is fixed length national character set- character datatype. This datatype uses CHAR length semantics, that is, the length of the NCHAR datatype column is defined in characters.

2)NVARCHAR2: It is variable length national character set- character datatype. This datatype uses CHAR length semantics, that is, the length of the NVARCHAR2 datatype column is defined in characters.

3)NCLOB: It stores national character set data up to four gigabytes. Data is always stored in UCS2 or AL16UTF16, even if the NLS_NCHAR_CHARACTERSET is UTF8.

If you use NCHAR/NVARCHAR2/NCLOB data type then, use the (N'...') syntax when coding these data type so that literals are denoted as being in the national character set by prefixing letter 'N'.

Below is an example.

SQL> create table t_test(col1 NVARCHAR2(30));

Table created.

SQL> insert into t_test values(N'This is NLS_NCHAR_CHARACTERSET');

1 row created.

Related Documents
Unicode characterset in Oracle database.
What is NLS_LANG environmental variable?
What is database character set and how to check it
Different ways to set up NLS parameters
What is national character set / NLS_NCHAR_CHARACTERSET?
What is character set and character set encoding

What is national character set / NLS_NCHAR_CHARACTERSET?

• The national character set is the character set which is defined in oracle database in addition to normal character set.

• The normal character set is defined by the parameter NLS_CHARACTERSET and the national character set is defined by the parameter NLS_NCHAR_CHARACTERSET.

• The national character set is used for data stored in NCHAR, NVARCHAR2 and NCLOB columns while the normal character set is used for data stored in CHAR, VARCHAR2, CLOB columns.

• You can get the value of national character set or NLS_NCHAR_CHARACTERSET by,

SQL> select value from nls_database_parameters where parameter='NLS_NCHAR_CHARACTERSET';

VALUE
----------------------------------------
AL16UTF16

SQL> select value$ from sys.props$ where name='NLS_NCHAR_CHARACTERSET';

VALUE$
--------------------------------------------------------------------------------
AL16UTF16

SQL> select property_value from database_properties where property_name
='NLS_NCHAR_CHARACTERSET';

PROPERTY_VALUE
--------------------------------------------------------------------------------
AL16UTF16

• NLS_NCHAR_CHARACTERSET is defined when the database is created and specified with the CREATE DATABASE command.
  

• The default value of NLS_NCHAR_CHARACTERSET is AL16UTF16.
  

• From Oracle 9i onwards the NLS_NCHAR_CHARACTERSET can have only 2 values, either UTF8 or AL16UTF16 and both are unicode character sets.
  

• National character set are always defined in CHAR length semantics and you cannot define them in BYTE. That means if you defines NCHAR(5) then 5 maximum characters can be stored regardless of how many bytes they can hold.
  

• Many one thinks that they need to use the NLS_NCHAR_CHARACTERSET to have UNICODE support in oracle but this is not true. One can always use UNICODE in either two ways. Storing data into NCHAR, NVARCHAR2 or NCLOB columns or you can perfectly use "normal" CHAR and VARCHAR2 columns for storing unicode in a database who has a AL32UTF8 / UTF8 NLS_CHARACTERSET.

Related Documents
Unicode characterset in Oracle database.
What is NLS_LANG environmental variable?
What is database character set and how to check it
Different ways to set up NLS parameters
Which datatypes use the National Character Set?
What is character set and character set encoding