About sys_Context Function

In Oracle/PLSQL, the sys_context function can be used to retrieve information about the Oracle environment.
The syntax for the sys_context function is:

sys_context( namespace, parameter, [ length ] )

namespace is an Oracle namespace that has already been created. If the namespace of 'USERENV' is used,
attributes describing the current Oracle session can be returned.
parameter is a valid attribute that has been set using the DBMS_SESSION.set_context procedure.length is optional.
It is the length of the return value in bytes. If this parameter is omitted or if an invalid entry is provided,
the sys_context function will default to 256 bytes.

The valid parameters for the namespace called 'USERENV' are as follows:

Parameter	Explanation	Return Length
AUDITED_CURSORID	Returns the cursor ID of the SQL that triggered the audit	N/A
AUTHENTICATION_DATA	Authentication data	256
AUTHENTICATION_TYPE	Describes how the user was authenticated. Can be one of the following values: Database, OS, Network, or Proxy	30
BG_JOB_ID	If the session was established by an Oracle background process, this parameter will return the Job ID. Otherwise, it will return NULL.	30
CLIENT_IDENTIFIER	Returns the client identifier (global context)	64
CLIENT_INFO	User session information	64
CURRENT_SCHEMA	Returns the default schema used in the current schema	30
CURRENT_SCHEMAID	Returns the identifier of the default schema used in the current schema	30
CURRENT_SQL	Returns the SQL that triggered the audit event	64
CURRENT_USER	Name of the current user	30
CURRENT_USERID	Userid of the current user	30
DB_DOMAIN	Domain of the database from the DB_DOMAIN initialization parameter	256
DB_NAME	Name of the database from the DB_NAME initialization parameter	30
ENTRYID	Available auditing entry identifier	30
EXTERNAL_NAME	External of the database user	256
FG_JOB_ID	If the session was established by a client foreground process, this parameter will return the Job ID. Otherwise, it will return NULL.	30
GLOBAL_CONTEXT_MEMORY	The number used in the System Global Area by the globally accessed context	N/A
HOST	Name of the host machine from which the client has connected	54
INSTANCE	The identifier number of the current instance	30
IP_ADDRESS	IP address of the machine from which the client has connected	30
ISDBA	Returns TRUE if the user has DBA privileges. Otherwise, it will return FALSE.	30
LANG	The ISO abbreviate for the language	62
LANGUAGE	The language, territory, and character of the session. In the following format: language_territory.characterset	52
NETWORK_PROTOCOL	Network protocol used	256
NLS_CALENDAR	The calendar of the current session	62
NLS_CURRENCY	The currency of the current session	62
NLS_DATE_FORMAT	The date format for the current session	62
NLS_DATE_LANGUAGE	The language used for dates	62
NLS_SORT	BINARY or the linguistic sort basis	62
NLS_TERRITORY	The territory of the current session	62
OS_USER	The OS username for the user logged in	30
PROXY_USER	The name of the user who opened the current session on behalf of SESSION_USER	30
PROXY_USERID	The identifier of the user who opened the current session on behalf of SESSION_USER	30
SESSION_USER	The database user name of the user logged in	30
SESSION_USERID	The database identifier of the user logged in	30
SESSIONID	The identifier of the auditing session	30
TERMINAL	The OS identifier of the current session	10

Applies To:

• Oracle 8i, Oracle 9i, Oracle 10g, Oracle 11g
  

For example:

sys_context('USERENV', 'NLS_DATE_FORMAT') would return 'RR-MM-DD'
sys_context('USERENV', 'NLS_SORT') would return 'BINARY'