sys

--sys_context SYS_CONTEXT('namespace', 'parameter' [, length ]) SYS_CONTEXT returns the value of parameter associated with the context namespace at the current instant. You can use this function in both SQL and PL/SQL statements. SYS_CONTEXT must be executed locally. The namespace must be a valid SQL identifier. The parameter name can be any string. It is not case sensitive, but it cannot exceed 30 bytes in length. Oracle provides the following built-in namespaces: USERENV - Describes the current session. The predefined parameters of namespace USERENV are listed in Table 5-11. SYS_SESSION_ROLES - Indicates whether a specified role is currently enabled for the session. This namespace is available starting with Oracle Database 11g Release 2 (11.2.0.4). parameter的值：

http://docs.oracle.com/cd/E11882_01/server.112/e41084/functions184.htm#SQLRF06117

EODA@PROD1> select SYS_CONTEXT('USERENV','LANGUAGE') language from dual; LANGUAGE ---------------------------------------------------------------------------------------------------- AMERICAN_AMERICA.AL32UTF8 EODA@PROD1> select SYS_CONTEXT('USERENV','CURRENT_USER') current_user from dual; CURRENT_USER ---------------------------------------------------------------------------------------------------- EODA EODA@PROD1> select sys_context('userenv', 'sid') from dual; SYS_CONTEXT('USERENV','SID') ---------------------------------------------------------------------------------------------------- 50