sys_context函数

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函数是Oracle提供的一个获取环境上下文信息的预定义函数。该函数用来返回一个指定namespace下的parameter值。该函数可以在SQL和PL/SQL语言中使用。

 

 

sys_context实际上就是一个Oracle存储和传递参数的容器访问函数。我们登入Oracle服务器，是带有会话信息session_info和其他一些属性信息。其中，有一些是Oracle预定义的，登录系统的时候自动填入到指定的变量中。还有一些是我们自己定义到其中，用于传递值使用的。

 

 

下面是sys_context函数的使用格式：

 

sys_context(‘namespace’,’parameter’{,length});

 

其中，namespace是存储信息的一个组group单位，namespace是按照类别进行分类的。一个namespace下可以有多个参数值，通过不同的parameter进行区分。namespace是预先定义好的SQL标识符，而parameter是可以任意大小写非敏感的字符串，不超过30位长度。

 

 

函数返回值为varchar2类型，长度默认为256位。如果需要限制这个默认值，可以数据length参数作为新的返回长度值。

 

设置namespace指定parameter值，可以使用dbms_session.set_context方法进行。

//自定义一个namespace，并且规定的设置的方法句柄；…………………….step 1

SQL> create context Test using set_test_context;

 

Context created

 

//定义方法…………………….step 2

create or replace procedure set_test_context

(

  vc_value in varchar2

)

is

begin

 dbms_session.set_context('Test','a1',vc_value);

end set_test_context;

 

//设置上值…………………….step 3

SQL> exec set_test_context('m');

 

PL/SQL procedure successfully completed

 

//获取这个值

SQL> select sys_context('Test','a1') from dual;

 

SYS_CONTEXT('TEST','A1')

------------------------------------

m

 

 

step1-3很重要，因为Test namespace为自定义的namespace，所以需要这样的设置，以确定权限所属。

 

 

sys_context函数最常用的就是userenv命名空间下的系列参数。下面是参数列表，摘自

http://hi.baidu.com/edeed/blog/item/28cba0ecaa6c8e3e269791bb.html；

 

Attribute

Return Value

ACTION

Identifies the position in the module (application name) and is set through the DBMS_APPLICATION_INFO package or OCI.

SELECTsys_context('USERENV', 'ACTION') FROM dual;

exec dbms_application_info.set_action('INSERTING');

SELECTsys_context('USERENV', 'ACTION') FROM dual;

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 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

BG_JOB_ID

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.

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 user.

SELECTsys_context('USERENV', 'CLIENT_IDENTIFIER') FROM dual;

exec dbms_session.set_identifier(USER || ' ' || SYSTIMESTAMP);

SELECTsys_context('USERENV', 'CLIENT_IDENTIFIER') FROM dual;

CLIENT_INFO

Returns user session information that can be stored by an application using the DBMS_APPLICATION_INFO package.

SELECTsys_context('USERENV', 'CLIENT_INFO') FROM dual;

exec dbms_application_info.set_client_info('TEST');

SELECTsys_context('USERENV', 'CLIENT_INFO') FROM dual;

CURRENT_BIND

The bind variables for fine-grained auditing

CURRENT_EDITION_ID

The name of the current edition

SELECTsys_context('USERENV', 'CURRENT_EDITION_ID') FROM dual;

CURRENT_EDITION_NAME

The name of the current edition

SELECTsys_context('USERENV', 'CURRENT_EDITION_NAME') FROM dual;

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.

SELECTsys_context('USERENV', 'CURRENT_SCHEMA') FROM dual;

CURRENT_SCHEMAID

Identifier of the default schema being used in the current session.

SELECTsys_context('USERENV', 'CURRENT_SCHEMAID') FROM dual;

SELECT user#
FROM sys.user$
WHERE name = USER;

CURRENT_SQL

Returns the first 4K bytes of the current SQL that triggered the fine-grained auditing event.

CURRENT_SQLn

CURRENT_SQLnattributes 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.

SELECTsys_context('USERENV', 'DB_DOMAIN') FROM dual;

DB_NAME

Name of the database as specified in the DB_NAME initialization parameter.

SELECTsys_context('USERENV', 'DB_NAME') FROM dual;

SELECT name, value
FROM gv$parameter
where name LIKE 'db%name';

DB_UNIQUE NAME

Name of the database as specified in the DB_UNIQUE_NAME initialization parameter.

SELECTsys_context('USERENV', 'DB_UNIQUE_NAME') FROM dual;

SELECT name, value
FROM gv$parameter
where name LIKE 'db%name';

ENTRYID

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.

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

The number used in the System Global Area by the globally accessed context.

SELECTsys_context('USERENV', 'GLOBAL_CONTEXT_MEMORY') FROM dual;

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.

SELECTsys_context('USERENV', 'HOST') FROM dual;

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

SELECTsys_context('USERENV', 'IDENTIFICATION_TYPE') FROM dual;

INSTANCE

The instance identification number of the current instance.

SELECTsys_context('USERENV', 'INSTANCE') FROM dual;

INSTANCE_NAME

The name of the instance.

SELECTsys_context('USERENV', 'INSTANCE_NAME') FROM dual;

IP_ADDRESS

IP address of the machine from which the client is connected.

ISDBA

TRUE if the session is SYS

SELECTsys_context('USERENV', 'ISDBA') FROM dual;

LANG

The ISO abbreviation for the language name, a shorter form. than the existing 'LANGUAGE' parameter.

SELECTsys_context('USERENV', 'LANG') FROM dual;

LANGUAGE

The language and territory currently used by your session, along with the database character set, in the form.:

language_territory.characterset.

SELECTsys_context('USERENV', 'LANGUAGE') FROM dual;

MODULE

The application name (module) set through the DBMS_APPLICATION_INFO package or OCI.

SELECTsys_context('USERENV', 'MODULE') FROM dual;

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.

SELECTsys_context('USERENV', 'NLS_CALENDAR') FROM dual;

NLS_CURRENCY

The currency of the current session.

SELECTsys_context('USERENV', 'NLS_CURRENCY') FROM dual;

NLS_DATE_FORMAT

The date format for the session.

SELECTsys_context('USERENV', 'NLS_DATE_FORMAT') FROM dual;

NLS_DATE_LANGUAGE

The language used for expressing dates.

SELECTsys_context('USERENV', 'NLS_DATE_LANGUAGE') FROM dual;

NLS_SORT

BINARY or the linguistic sort basis.

SELECTsys_context('USERENV', 'NLS_SORT') FROM dual;

NLS_TERRITORY

The territory of the current session.

SELECTsys_context('USERENV', 'NLS_TERRITORY') FROM dual;

OS_USER

Operating system username of the client process that initiated the database session.

SELECTsys_context('USERENV', 'OS_USER') FROM dual;

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.

SELECTsys_context('USERENV', 'SERVER_HOST') FROM dual;

SERVICE_NAME

The name of the service to which a given session is connected.

SELECTsys_context('USERENV', 'SERVICE_NAME') FROM dual;

SESSION_USER

Database user name by which the current user is authenticated. This value remains the same throughout the duration of the session.

SELECTsys_context('USERENV', 'SESSION_USER') FROM dual;

SESSION_USERID

Identifier of the database user name by which the current user is authenticated.

SELECTsys_context('USERENV', 'SESSION_USERID') FROM dual;

SESSIONID

The auditing session identifier. You cannot use this option in distributed SQL statements. This is the equivalent to the AUDSID column ingv$session.

SELECTsys_context('USERENV', 'SESSIONID') FROM dual;

SID

The session number (different from the session ID).

SELECTsys_context('USERENV', 'SID') FROM dual;

STATEMENTID

The auditing statement identifier. STATEMENTID represents the number of SQL statements audited in a given session.

TERMINAL

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.)

SELECTsys_context('USERENV', 'TERMINAL') FROM dual;

 

 

例子：

 

SQL> select sys_context('userenv','ip_address') from dual;

 

SYS_CONTEXT('USERENV','IP_ADDR

-----------------------------------

169.254.94.86