1  –  schema-expression

    Specifies the name of the default schema for a multischema
    database. If you omit the schema name when you specify an object
    in a multischema database, SQL uses the default schema name. If
    you do not specify a default schema name, the default uses the
    user name of the current user.

    See the User_Supplied_Names HELP topic for more information on
    schemas.

2  –  schema-parameter

    Specifies a host language variable in precompiled SQL or a formal
    parameter in an SQL module language procedure that specifies
    the default schema. The schema parameter must contain a schema
    expression.

3  –  schema-parameter-marker

    Specifies a parameter marker (?)  in a dynamic SQL statement.
    The schema parameter marker refers to a parameter that specifies
    the default schema. The schema parameter marker must specify a
    parameter that contains a schema expression.

4  –  schema-string-literal

    Specifies a character string literal that specifies the
    default schema. The schema string literal must contain a schema
    expression enclosed within single quotation marks.