Term: SYS_CONTEXT

Definition:
In Oracle PL/SQL, SYS_CONTEXT is used to get relevant information about the Oracle database environment. It accepts three parameters:, NAMESPACE, PARAMETER and LENGTH. Oracle's built in Namespace 'USERENV' is an SQL identifier, used to retrieve current session information. Parameters are the information variables which are associated to the Namespace and which have been set using the DBMS_SESSION.SET_CONTEXT procedure.
It returns character-based output whose length can be set by the LENGTH parameter. The valid range for the LENGTH parameter is from 1 to 4000.

The list below shows latest USERENV namespace parameters available in Oracle 11g which provide current session information in the database:

Parameter	Return Value	Return Length (bytes)
`ACTION`	Identifies the position in the module (application name) and is set through the `DBMS_APPLICATION_INFO` package or OCI.	32
`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`.	NA
`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.	256
`AUTHENTICATION_TYPE`	How the user was authenticated: `DATABASE`: user name/password authentication `OS`: operating system external user authentication `NETWORK`: network protocol or ANO authentication `PROXY`: OCI proxy connection authentication	30
`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.	64
`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.	64
`CLIENT_INFO`	Returns up to 64 bytes of user session information that can be stored by an application using the `DBMS_APPLICATION_INFO` package.	64
`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.	30
`CURRENT_SCHEMAID`	Identifier of the default schema being used in the current session.	30
`CURRENT_SQL` `CURRENT_SQL``n`	`CURRENT_SQL` returns the first 4K bytes of the current SQL that triggered the fine-grained auditing event. The `CURRENT_SQL``n` 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.	4
`CURRENT_USER`	This attribute is being deprecated. Use the `SESSION_USER` attribute instead.	30
`CURRENT_USERID`	This attribute is being deprecated. Use the `SESSION_USERID` attribute instead.	30
`DB_DOMAIN`	Domain of the database as specified in the `DB_DOMAIN` initialization parameter.	256
`DB_NAME`	Name of the database as specified in the `DB_NAME` initialization parameter.	30
`DB_UNIQUE_NAME`	Name of the database as specified in the `DB_UNIQUE_NAME` initialization parameter.	30
`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.	30
`EXTERNAL_NAME`	External name of the database user. For SSL authenticated sessions using v.503 certificates, this parameter returns the distinguished name (DN) stored in the user certificate.	256
`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.	30
`GLOBAL_CONTEXT_MEMORY`	Returns the number being used in the System Global Area by the globally accessed context.	NA
`HOST`	Name of the host machine from which the client has connected.	54
`INSTANCE`	The instance identification number of the current instance.	30
`IP_ADDRESS`	IP address of the machine from which the client is connected.	30
`ISDBA`	Returns `TRUE` if the user has been authenticated as having DBA privileges either through the operating system or through a password file.	30
`LANG`	The ISO abbreviation for the language name, a shorter form than the existing '`LANGUAGE`' parameter.	62
`LANGUAGE`	The language and territory currently used by your session, along with the database character set, in this form: language_territory.characterset	52
`MODULE`	The application name (module) set through the `DBMS_APPLICATION_INFO` package or OCI.	48
`NETWORK_PROTOCOL`	Network protocol being used for communication, as specified in the '`PROTOCOL`=`protocol`' portion of the connect string.	256
`NLS_CALENDAR`	The current calendar of the current session.	62
`NLS_CURRENCY`	The currency of the current session.	62
`NLS_DATE_FORMAT`	The date format for the session.	62
`NLS_DATE_LANGUAGE`	The language used for expressing dates.	62
`NLS_SORT`	`BINARY` or the linguistic sort basis.	62
`NLS_TERRITORY`	The territory of the current session.	62
`OS_USER`	Operating system user name of the client process that initiated the database session.	30
`PROXY_USER`	Name of the database user who opened the current session on behalf of `SESSION_USER`.	30
`PROXY_USERID`	Identifier of the database user who opened the current session on behalf of `SESSION_USER`.	30
`SERVICE_NAME`	The name of the service to which a given session is connected.	64
`SESSION_USER`	Database user name by which the current user is authenticated. This value remains the same throughout the duration of the session.	30
`SESSION_USERID`	Identifier of the database user name by which the current user is authenticated.	30
`SESSIONID`	The auditing session identifier. You cannot use this attribute in distributed SQL statements.	30
`STATEMENTID`	The auditing statement identifier. `STATEMENTID` represents the number of SQL statements audited in a given session.	NA
`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.)	10

Example Syntax:

SYS_CONTEXT ( ' namespace ' , ' parameter ', length)

Example Usage:

The SQL queries below display the parameter values for CURRENT_SCHEMA, DB_NAME and LANGUAGE in the USERENV namespace.

SQL> SELECT SYS_CONTEXT('USERENV', 'CURRENT_SCHEMA') FROM dual;



SYS_CONTEXT('USERENV','CURRENT_SCHEMA')

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

SCOTT



SQL> SELECT SYS_CONTEXT('USERENV', 'DB_NAME') FROM dual;



SYS_CONTEXT('USERENV','DB_NAME')

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

SYSTEM



SQL> SELECT SYS_CONTEXT('USERENV', 'LANGUAGE') FROM dual;



SYS_CONTEXT('USERENV','LANGUAGE')

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