SYS_CONTEXT用法

select SYS_CONTEXT('USERENV', 'TERMINAL') terminal,
       SYS_CONTEXT('USERENV', 'LANGUAGE') language,
       SYS_CONTEXT('USERENV', 'SESSIONID') sessionid,
       SYS_CONTEXT('USERENV', 'INSTANCE') instance,
       SYS_CONTEXT('USERENV', 'ENTRYID') entryid,
       SYS_CONTEXT('USERENV', 'ISDBA') isdba,
       SYS_CONTEXT('USERENV', 'NLS_TERRITORY') nls_territory,
       SYS_CONTEXT('USERENV', 'NLS_CURRENCY') nls_currency,
       SYS_CONTEXT('USERENV', 'NLS_CALENDAR') nls_calendar,
       SYS_CONTEXT('USERENV', 'NLS_DATE_FORMAT') nls_date_format,
       SYS_CONTEXT('USERENV', 'NLS_DATE_LANGUAGE') nls_date_language,
       SYS_CONTEXT('USERENV', 'NLS_SORT') nls_sort,
       SYS_CONTEXT('USERENV', 'CURRENT_USER') current_user,
       SYS_CONTEXT('USERENV', 'CURRENT_USERID') current_userid,
       SYS_CONTEXT('USERENV', 'SESSION_USER') session_user,
       SYS_CONTEXT('USERENV', 'SESSION_USERID') session_userid,
       SYS_CONTEXT('USERENV', 'PROXY_USER') proxy_user,
       SYS_CONTEXT('USERENV', 'PROXY_USERID') proxy_userid,
       SYS_CONTEXT('USERENV', 'DB_DOMAIN') db_domain,
       SYS_CONTEXT('USERENV', 'DB_NAME') db_name,
       SYS_CONTEXT('USERENV', 'HOST') host,
       SYS_CONTEXT('USERENV', 'OS_USER') os_user,
       SYS_CONTEXT('USERENV', 'EXTERNAL_NAME') external_name,
       SYS_CONTEXT('USERENV', 'IP_ADDRESS') ip_address,
       SYS_CONTEXT('USERENV', 'NETWORK_PROTOCOL') network_protocol,
       SYS_CONTEXT('USERENV', 'BG_JOB_ID') bg_job_id,
       SYS_CONTEXT('USERENV', 'FG_JOB_ID') fg_job_id,
       SYS_CONTEXT('USERENV', 'AUTHENTICATION_TYPE') authentication_type,
       SYS_CONTEXT('USERENV', 'AUTHENTICATION_DATA') authentication_data
  from dual

SYS_CONTEXT

Syntax

Description of the illustration sys_context.gif

Purpose

SYS_CONTEXT returns the value of parameter associated with the context namespace. You can use this function in both SQL and PL/SQL statements.

For namespace and parameter, you can specify either a string or an expression that resolves to a string designating a namespace or an attribute. The context namespace must already have been created, and the associated parameter and its value must also have been set using the DBMS_SESSION.set_context procedure. 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.

The datatype of the return value is VARCHAR2. The default maximum size of the return value is 256 bytes. You can override this default by specifying the optional length parameter, which must be a NUMBER or a value that can be implicitly converted to NUMBER. The valid range of values is 1 to 4000 bytes. If you specify an invalid value, then Oracle Database ignores it and uses the default.

Oracle provides a built-in namespace called USERENV, which describes the current session. The predefined parameters of namespace USERENV are listed in Table 5-11.

See Also:

• Oracle Database Application Developer's Guide - Fundamentals for information on using the application context feature in your application development

• CREATE CONTEXT for information on creating user-defined context namespaces

• PL/SQL Packages and Types Reference for information on the DBMS_SESSION.set_context procedure

Examples

The following statement returns the name of the user who logged onto the database:

CONNECT OE/OE
SELECT SYS_CONTEXT ('USERENV', 'SESSION_USER')
FROM DUAL;
SYS_CONTEXT ('USERENV', 'SESSION_USER')
------------------------------------------------------
OE

The following hypothetical example returns the group number that was set as the value for the attribute group_no in the PL/SQL package that was associated with the context hr_apps when hr_apps was created:

SELECT SYS_CONTEXT ('hr_apps', 'group_no') "User Group"
FROM DUAL;

Table 5-11 Predefined Parameters of Namespace USERENV

Parameter	Return Value
ACTION	Identifies the position in the module (application name) and is set through the DBMS_APPLICATION_INFO package or OCI.
AUDITED_CURSORID	Returns the cursor ID of the SQL that triggered the audit. This parameter is not valid in a fine-grained auditing environment. If you specify it in such an environment, Oracle Database always returns NULL.
AUTHENTICATED_IDENTITY	Returns the identity used in authentication. In the list that follows, the type of user is followed by the value returned: Kerberos-authenticated enterprise user: kerberos principal name Kerberos-authenticated external user : kerberos principal name; same as the schema name SSL-authenticated enterprise user: the DN in the user's PKI certificate SSL-authenticated external user: the DN in the user's PKI certificate Password-authenticated enterprise user: nickname; same as the login name Password-authenticated database user: the database username; same as the schema name OS-authenticated external user: the external operating system user name Radius/DCE-authenticated external user: the schema name Proxy with DN : Oracle Internet Directory DN of the client Proxy with certificate: certificate DN of the client Proxy with username: database user name if client is a local database user; nickname if client is an enterprise user. SYSDBA/SYSOPER using Password File: login name SYSDBA/SYSOPER using OS authentication: operating system user name
AUTHENTICATION_DATA	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 Database implements such a change.
AUTHENTICATION_METHOD	Returns the method of authentication. In the list that follows, the type of user is followed by the method returned: Password-authenticated enterprise user, local database user, or SYSDBA/SYSOPER using Password File; proxy with username using password: PASSWORD Kerberos-authenticated enterprise or external user: KERBEROS SSL-authenticated enterprise or external user: SSL Radius-authenticated external user: RADIUS OS-authenticated external user or SYSDBA/SYSOPER: OS DCE-authenticated external user: DCE Proxy with certificate, DN, or username without using password: NONE You can use IDENTIFICATION_TYPE to distinguish between external and enterprise users when the authentication method is Password, Kerberos, or SSL.
BG_JOB_ID	Job ID of the current session if it was established by an Oracle Database background process. Null if the session was not established by a background process.
CLIENT_IDENTIFIER	Returns an identifier that is set by the application through the DBMS_SESSION.SET_IDENTIFIER procedure, the OCI attribute OCI_ATTR_CLIENT_IDENTIFIER, or the Java class Oracle.jdbc.OracleConnection.setClientIdentifier. This attribute is used by various database components to identify lightweight application users who authenticate as the same database user.
CLIENT_INFO	Returns up to 64 bytes of user session information that can be stored by an application using the DBMS_APPLICATION_INFO package.
CURRENT_BIND	The bind variables for fine-grained auditing.
CURRENT_SCHEMA	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.
CURRENT_SCHEMAID	Identifier of the default schema being used in the current session.
CURRENT_SQL CURRENT_SQLn	CURRENT_SQL returns the first 4K bytes of the current SQL that triggered the fine-grained auditing event. The CURRENT_SQLn attributes return subsequent 4K-byte increments, where n can be an integer from 1 to 7, inclusive. CURRENT_SQL1 returns bytes 4K to 8K; CURRENT_SQL2 returns bytes 8K to 12K, and so forth. You can specify these attributes only inside the event handler for the fine-grained auditing feature.
CURRENT_SQL_LENGTH	The length of the current SQL statement that triggers fine-grained audit or row-level security (RLS) policy functions or event handlers. Valid only inside the function or event handler.
DB_DOMAIN	Domain of the database as specified in the DB_DOMAIN initialization parameter.
DB_NAME	Name of the database as specified in the DB_NAME initialization parameter.
DB_UNIQUE_NAME	Name of the database as specified in the DB_UNIQUE_NAME initialization parameter.
ENTRYID	The current audit entry number. The audit entryid sequence is shared between fine-grained audit records and regular audit records. You cannot use this attribute in distributed SQL statements. The correct auditing entry identifier can be seen only through an audit handler for standard or fine-grained audit.
ENTERPRISE_IDENTITY	Returns the user's enterprise-wide identity: For enterprise users: the Oracle Internet Directory DN. For external users: the external identity (Kerberos principal name, Radius and DCE schema names, OS user name, Certificate DN). For local users and SYSDBA/SYSOPER logins: NULL. The value of the attribute differs by proxy method: For a proxy with DN: the Oracle Internet Directory DN of the client For a proxy with certificate: the certificate DN of the client for external users; the Oracle Internet Directory DN for global users For a proxy with username: the Oracle Internet Directory DN if the client is an enterprise users; NULL if the client is a local database user.
FG_JOB_ID	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.
GLOBAL_CONTEXT_MEMORY	Returns the number being used in the System Global Area by the globally accessed context.
GLOBAL_UID	Returns the global user ID from Oracle Internet Directory for Enterprise User Security (EUS) logins; returns null for all other logins.
HOST	Name of the host machine from which the client has connected.
IDENTIFICATION_TYPE	Returns the way the user's schema was created in the database. Specifically, it reflects the IDENTIFIED clause in the CREATE/ALTER USER syntax. In the list that follows, the syntax used during schema creation is followed by the identification type returned: IDENTIFIED BY password: LOCAL IDENTIFIED EXTERNALLY: EXTERNAL IDENTIFIED GLOBALLY: GLOBAL SHARED IDENTIFIED GLOBALLY AS DN: GLOBAL PRIVATE
INSTANCE	The instance identification number of the current instance.
INSTANCE_NAME	The name of the instance.
IP_ADDRESS	IP address of the machine from which the client is connected.
ISDBA	Returns TRUE if the user has been authenticated as having DBA privileges either through the operating system or through a password file.
LANG	The ISO abbreviation for the language name, a shorter form than the existing 'LANGUAGE' parameter.
LANGUAGE	The language and territory currently used by your session, along with the database character set, in this form: language_territory.characterset
MODULE	The application name (module) set through the DBMS_APPLICATION_INFO package or OCI.
NETWORK_PROTOCOL	Network protocol being used for communication, as specified in the 'PROTOCOL=protocol' portion of the connect string.
NLS_CALENDAR	The current calendar of the current session.
NLS_CURRENCY	The currency of the current session.
NLS_DATE_FORMAT	The date format for the session.
NLS_DATE_LANGUAGE	The language used for expressing dates.
NLS_SORT	BINARY or the linguistic sort basis.
NLS_TERRITORY	The territory of the current session.
OS_USER	Operating system user name of the client process that initiated the database session.
POLICY_INVOKER	The invoker of row-level security (RLS) policy functions.
PROXY_ENTERPRISE_IDENTITY	Returns the Oracle Internet Directory DN when the proxy user is an enterprise user.
PROXY_GLOBAL_UID	Returns the global user ID from Oracle Internet Directory for Enterprise User Security (EUS) proxy users; returns NULL for all other proxy users.
PROXY_USER	Name of the database user who opened the current session on behalf of SESSION_USER.
PROXY_USERID	Identifier of the database user who opened the current session on behalf of SESSION_USER.
SERVER_HOST	The host name of the machine on which the instance is running.
SERVICE_NAME	The name of the service to which a given session is connected.
SESSION_USER	For enterprises users, returns the schema. For other users, returns the database user name by which the current user is authenticated. This value remains the same throughout the duration of the session.
SESSION_USERID	Identifier of the database user name by which the current user is authenticated.
SESSIONID	The auditing session identifier. You cannot use this attribute in distributed SQL statements.
SID	The session number (different from the session ID).
STATEMENTID	The auditing statement identifier. STATEMENTID represents the number of SQL statements audited in a given session. You cannot use this attribute in distributed SQL statements. The correct auditing statement identifier can be seen only through an audit handler for standard or fine-grained audit.
TERMINAL	The operating system identifier for the client of the current session. In distributed SQL statements, this attribute 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.)

Table 5-12 lists the parameters of namespace USERENV that have been deprecated. Oracle suggests that you use the alternatives suggested in the Comments column.

Table 5-12 Deprecated Parameters of Namespace USERENV

Parameter	Comments
AUTHENTICATION_TYPE	This parameter returned a value indicating how the user was authenticated. The same information is now available from the new AUTHENTICATION_METHOD parameter combined with IDENTIFICATION_TYPE.
CURRENT_USER	Use the SESSION_USER parameter instead.
CURRENT_USERID	Use the SESSION_USERID parameter instead.
EXTERNAL_NAME	This parameter returned the external name of the user. More complete information can now be obtained from the AUTHENTICATED_IDENTITY and ENTERPRISE_IDENTITY parameter.