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what is sys_context in oracle – for the new oracle dba





you are a new oracle dba and you would like to know about sys_context.

SYS_CONTEXT

Syntax

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 on

page 5-177.

See Also:

Oracle Database Application Developer’s Guide – Fundamentals for

information on using the application context feature in your

application development

■ CREATE CONTEXT on page 14-9 for information on creating

user-defined context namespaces

Oracle Database PL/SQL Packages and Types Reference for

information on the DBMS_SESSION.set_context procedure

SYS_CONTEXT ( ’ namespace ’ , ’ parameter ’

, length

)

SYS_CONTEXT

Functions 5-177

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.

SYS_CONTEXT

5-178 Oracle Database SQL Reference

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.

Table 5–11 (Cont.) Predefined Parameters of Namespace USERENV

Parameter Return Value

SYS_CONTEXT

Functions 5-179

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.

Table 5–11 (Cont.) Predefined Parameters of Namespace USERENV

Parameter Return Value

SYS_CONTEXT

5-180 Oracle Database SQL Reference

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.

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 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.

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