1  –  DEFAULT value-expr

    Specifies the default value of a parameter for a function or
    procedure defined with mode IN. If you omit this parameter or if
    the CALL statement argument list or function invocation specifies
    the DEFAULT keyword, then the value-expr specified with this
    clause is used. The parameter uses NULL as the default if you do
    not specify a value expression explicitly.

2  –  FUNCTION

    Declares a function definition.

    A function optionally accepts a list of IN parameters, always
    returns a value, and is referenced by name as an element of a
    value expression.

3  –  LANGUAGE_SQL

    Names the language that calls the routine.

4  –  mechanism-clause

    Defines the passing mechanism for an external routine. The
    following list describes the passing mechanisms.

    o  BY DESCRIPTOR

       Allows passing character data with any parameter access mode
       to routines compiled by language compilers that implement the
       OpenVMS calling standard.

    o  BY LENGTH

       The LENGTH passing mechanism is the same as the DESCRIPTOR
       passing mechanism.

    o  BY REFERENCE

       Allows passing data with any parameter access mode as a
       reference to the actual data.

       This is the default passing mechanism for parameters. This
       is also the default passing mechanism for a function value
       returning character data.

    o  BY VALUE

       Allows passing data with the IN parameter access mode to a
       routine as a value and allows functions to return a value.

       This is the default passing mechanism for a function value
       returning noncharacter data.

5  –  parameter-list

    The optional parameters of the routine. For each parameter
    you can specify a parameter access mode (IN, OUT, and INOUT),
    a parameter name, a data type, and a passing mechanism (by
    DESCRIPTOR, LENGTH, REFERENCE, or VALUE).

    The parameter access mode (IN, OUT, and INOUT) is optional and
    specifies how the parameter is accessed (whether it is read,
    written, or both). IN signifies read only, OUT signifies write
    only, and INOUT signifies read and write. The parameter access
    mode defaults to IN.

    Only the IN parameter access mode may be specified with
    parameters to a function. Any of the parameter access modes (IN,
    OUT, and INOUT) may be specified with parameters to a procedure.

    The parameter name is prefixed with a colon (:).  The parameter
    name must be unique within the routine parameters.

    The data type is required and describes the type of parameter
    using either an SQL data type or a domain name.

    You cannot declare a parameter as the LIST OF BYTE VARYING data
    type.

6  –  PROCEDURE

    Declares a procedure definition.

    A procedure optionally accepts a list of IN, OUT, or INOUT
    parameters, and is referenced by name in a CALL statement.

7  –  RETURNS

    Describes a function (returned) value. You can specify a data
    type and a passing mechanism (BY DESCRIPTOR, LENGTH, REFERENCE,
    or VALUE). The function value is, by definition, an OUT access
    mode value.

    The data type is required and describes the type of parameter
    using either an SQL data type or a domain name.

    You cannot declare a function value as the LIST OF BYTE VARYING
    data type.

8  –  routine-name

    The name of the external routine. The name must be unique among
    external and stored routines in the schema and can be qualified
    with an alias or, in a multischema database, a schema name.

9  –  STORED_NAME_IS

    The name that Oracle Rdb uses to access the routine when defined
    in a multischema database. The stored name allows you to access
    multischema definitions using interfaces that do not recognize
    multiple schemas in one database. You cannot specify a stored
    name for a routine in a database that does not allow multiple
    schemas. For more information about stored names, see Stored
    Names.