用法：SELECT sys_context('USERENV', '
用法：SELECT sys_context('USERENV', '
Data being used to authenticate the login user. For X.503 certificate authenticated sessions, this field returns the context of the certificate in HEX2 format.
Note: You can change the return value of the AUTHENTICATION_DATA attribute using the length parameter of the syntax. Values of up to 4000 are accepted. This is the only attribute of USERENV for which Oracle implements such a change.
How the user was authenticated:
DATABASE: username/password authentication
OS: operating system external user authentication
NETWORK: network protocol or ANO authentication
PROXY: OCI proxy connection authentication
Job ID of the current session if it was established by an Oracle background process. Null if the session was not established by a background process.
Returns up to 64 bytes of user session information that can be stored by an application using the DBMS_APPLICATION_INFO package.
Name of the default schema being used in the current schema. This value can be changed during the session with an ALTER SESSION SET CURRENT_SCHEMA statement.
Identifier of the default schema being used in the current session.
The name of the user whose privilege the current session is under.
User ID of the user whose privilege the current session is under.
Domain of the database as specified in the DB_DOMAIN initialization parameter.
Name of the database as specified in the DB_NAME initialization parameter.
The available auditing entry identifier. You cannot use this option in distributed SQL statements. To use this keyword in USERENV, the initialization parameter AUDIT_TRAIL must be set to true.
External name of the database user. For SSL authenticated sessions using v.503 certificates, this field returns the distinguished name (DN) stored in the user certificate.
Job ID of the current session if it was established by a client foreground process. Null if the session was not established by a foreground process.
Name of the host machine from which the client has connected.
The instance identification number of the current instance.
IP address of the machine from which the client is connected.
TRUE if you are logged on as SYS.
The ISO abbreviation for the language name, a shorter form than the existing 'LANGUAGE' parameter.
The language and territory currently used by your session, along with the database character set, in the form:language_territory.characterset.
Network protocol being used for communication, as specified in the 'PROTOCOL=protocol' portion of the connect string.
The current calendar of the current session.
The currency of the current session.
The date format for the session.
The language used for expressing dates.
or the linguistic sort basis.
The territory of the current session.
Operating system username of the client process that initiated the database session.
Name of the database user who opened the current session on behalf of SESSION_USER.
Identifier of the database user who opened the current session on behalf of SESSION_USER.
Database user name by which the current user is authenticated. This value remains the same throughout the duration of the session.
Identifier of the database user name by which the current user is authenticated.
The auditing session identifier. You cannot use this option in distributed SQL statements.
The operating system identifier for the client of the current session. In distributed SQL statements, this option returns the identifier for your local session. In a distributed environment, this is supported only for remote SELECT statements, not for remote INSERT, UPDATE, or DELETE operations.
(The return length of this parameter may vary by operating system.)
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